Fuel markers and methods of producing and using same

ABSTRACT

A method of forming a composition comprising contacting a fuel and at least one compound of Formula I: 
                         
wherein X is carbon, oxygen, or sulfur; R 1  and R 2  each independently are hydrogen, a C 1  to C 20  alkyl, or a C 6  to C 10  aryl; R 3  and R 3′  each independently are hydrogen or a C 1  to C 4  alkyl; R 4  and R 4′  each independently are hydrogen, a C 1  to C 4  alkyl, a C 4  to C 10  cycloalkyl, or a C 6  to C 10  aryl; R 5  and R 5′  each independently are a C 4  to C 10  alkyl; R 6  and R 6′  each independently are hydrogen or a C 1  to C 6  alkyl; and R 7  and R 7′  each independently are hydrogen or C 1  to C 4  alkyl; and wherein the compound of Formula I when subjected to GC-MS using electron ionization at greater than 70 eV produces at least one ion having a mass-to-charge ratio of 300 to 600.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a non-provisional of and claims priority toU.S. Provisional Application Nos. 62/136,068 filed Mar. 20, 2015 and62/194,088, filed on Jul. 17, 2015 and both entitled “Fuel Markers andMethods of Producing and Using Same,” each of which is incorporated byreference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates to fuel compositions, more specificallymarked fuel compositions and methods of producing and using same.

BACKGROUND

Fuels represent a crucial energy supply and an important revenue source.Based on their provenience and quality (e.g., different grades or typesof fuel), fuels can be differentially priced, such as taxed fuel andsubsidized fuel or tax-free fuel; kerosene; diesel fuel; low-octanegasoline; high-octane gasoline; etc. Fuels can be differentially pricedfor a variety of reasons. In some countries, liquid fuel, such as dieselfuel, kerosene, and liquefied petroleum gas, is subsidized or sold belowmarket rates to provide more widespread access to resources. Fuel canalso be subsidized to protect certain industry sectors, such as publictransportation.

Fuel adulteration is a clandestine and profit-oriented operation that isconducted for financial gain, which operation is detrimental to therightful owner. Sometimes, fuels can be adulterated by mixing togetherfuels from different sources to obscure the origin of one or more of thefuels. Other times, adulterated fuels can be obtained by mixing higherpriced fuel with lower priced fuel (e.g., lower grade fuel) oradulterants such as solvents. In some cases, subsidized fuel can bepurchased and then re-sold, sometimes illegally, at a higher price. Forexample, subsidized fuel can be purchased and then mixed with other fuelto disguise the origin of the subsidized fuel.

Fuel markers can be added to fuels to establish ownership and/or originof fuel. However, some markers placed in fuel for authentication cansometimes be at least partially removed to disguise the origin of thefuel. While some methods have employed the use of deuterated structuresas fuel markers, such methods do not use of deuterated isotopologues toimprove the accuracy of analysis.

Fuel adulteration can be assessed by determining the presence andconcentration of fuel markers in a fuel sample via a variety ofanalytical techniques, such as gas chromatography (GC), massspectrometry (MS), etc. Fuel markers can interact with their immediateenvironment (e.g., matrix), such as fuel, solvent, masking agents, etc.,surrounding the marker, and the effect of the matrix can hinder theanalysis of a fuel sample for determining whether a fuel is adulteratedor not. While most prominently reported in trace level analysis ofpesticide residues, matrix effects have been attributed to matrixcomponents which cannot be efficiently separated from analytes ofinterest via a specified sample preparation methodology.

There have been a variety of approaches to mitigate matrix effects, suchas for example pulsed inlet conditions, matrix matched standards,inclusion of analyte protectants in analytical samples, etc. While theseapproaches could improve detectability of target analytes (e.g., fuelmarkers) in some instances, their application to routine analyses provesrather complicated from a practical point of view. These approaches areusually neither generally applicable to a wide variety of chemicalclasses of fuel marker, nor desirable as they would add significantcost, time and complexity to the analysis.

Another approach to mitigate matrix effects can employ “matrix matchedstandards,” where standards can be prepared from the same matrix to beanalyzed. While this approach can represent a way to reliably correctfor matrix effects, a diverse matrix in combination with the lack of apriori knowledge of what problematic components are present in thematrix can prevent this approach from being an effective solution.

Yet another approach to mitigate matrix effects can employ analytespiking (also known as “method of standard addition”), which entailsadding known amounts of a standard to one or more aliquots of an unknownsample. This approach can generate a standard curve where they-intercept of the linear regression fit of the collected datarepresents the endogenous concentration of the analyte (e.g., fuelmarker) in the sample. While theoretically this approach could work,practically it entails too high of a cost in terms of time (requires 2-4additional analyses per unknown sample) and the analysis of the data canbe considered too complex for the practical purpose of fuelauthentication.

Existing analytical approaches to determine fuel adulteration andmitigate matrix effects all have significant limitations that precludetheir utility in fuel authentication. Thus, there is an ongoing need todevelop and/or improve fuel markers and methods for detecting thesemarkers.

BRIEF SUMMARY

Disclosed herein is a method of forming a composition comprisingcontacting (a) a fuel and (b) at least one compound characterized byFormula I:

wherein X can be carbon (C), oxygen (O), or sulfur (S); R¹ and R² caneach independently be hydrogen, a C₁ to C₂₀ alkyl group, or a C₆ to C₁₀aryl group; R³ and R^(3′) can each independently be hydrogen or a C₁ toC₄ alkyl group; R⁴ and R^(4′) can each independently be hydrogen, a C₁to C₄ alkyl group, a C₄ to C₁₀ cycloalkyl group, or a C₆ to C₁₀ arylgroup; R⁵ and R^(5′) can each independently be a C₄ to C₁₀ alkyl group;R⁶ and R^(6′) can each independently be hydrogen or a C₁ to C₆ alkylgroup; and R⁷ and R^(7′) can each independently be hydrogen or a C₁ toC₄ alkyl group; and wherein the compound characterized by Formula I whensubjected to gas chromatography-mass spectrometry (GC-MS) using electronionization produces at least one ion having a mass-to-charge ratio offrom about 300 to about 600 at an ionization energy of equal to orgreater than about 70 eV.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure andadvantages thereof, reference will now be made to the accompanyingdrawings/figures in which:

FIG. 1 displays a graph of calculated fuel marker concentrations forseveral diesel fuel samples;

FIG. 2 displays ion chromatograms for fuel markers in different dieselfuel samples;

FIG. 3A displays ion chromatograms of a fuel marker in different dieselfuel samples prior to solid phase extraction; and

FIG. 3B displays ion chromatograms of a fuel marker in different dieselfuel samples subsequent to solid phase extraction.

DETAILED DESCRIPTION

Disclosed herein are marked fuel compositions and methods of determiningadulteration of same. In an embodiment, a marked fuel composition cancomprise a fuel and a fuel marker, wherein the fuel marker comprises atleast one compound characterized by Formula I:

wherein X can be carbon (C), oxygen (O), or sulfur (S); R¹ and R² caneach independently be hydrogen, a C₁ to C₂₀ alkyl group, or a C₆ to C₁₀aryl group; R³ and R^(3′) can each independently be hydrogen or a C₁ toC₄ alkyl group; R⁴ and R^(4′) can each independently be hydrogen, a C₁to C₄ alkyl group, a C₄ to C₁₀ cycloalkyl group, or a C₆ to C₁₀ arylgroup; R⁵ and R^(5′) can each independently be a C₄ to C₁₀ alkyl group;R⁶ and R^(6′) can each independently be hydrogen or a C₁ to C₆ alkylgroup; and R⁷ and R^(7′) can each independently be hydrogen or a C₁ toC₄ alkyl group. The compound characterized by Formula I can be furthersubjected to gas chromatography-mass spectrometry (GC-MS) using electronionization, wherein the compound characterized by Formula I produces atleast one ion having a mass-to-charge ratio of from about 300 to about600 at an ionization energy of equal to or greater than about 70 eV.

In an embodiment, a method of the present disclosure can comprisecontacting (a) a fuel and (b) at least one compound characterized byFormula I to yield a marked fuel composition. In an embodiment, themethod can further comprise subjecting the marked fuel composition to ananalytical technique for determining adulteration of the fuel. As usedherein, “adulteration” of a fuel refers to altering, mixing, diluting,laundering, etc., of the fuel. In some cases, a fuel (e.g., a fuel taxedat a higher rate) can be combined (e.g., illegally) “as is” with anotherfuel (e.g., an untaxed fuel or fuel taxed at a lower rate) or solvent toform an adulterated (e.g., altered, mixed, diluted, laundered, etc.)fuel. For example, a fuel can be mixed with one or more other fuels,solvents, and the like, or combinations thereof. If undetected, theadulterated fuel can be sold, sometimes illegally, at the price of thefuel taxed at the higher rate to yield a profit. In some instances, theadulterated fuel can be potentially hazardous for the user, such as forexample when a hazardous solvent is used for adulterating the fuel. Inother instances, the fuel can be treated or “laundered” in an attempt toremove identifying features such as markers from the fuel (e.g., todisguise the origin of the fuel, the amount of tax paid on the fuel,etc.) before the fuel is mixed with another fuel to form an adulteratedfuel.

In an embodiment, a method of determining adulteration of a fuelcomprises subjecting to an analytical technique a marked fuel mixturecomprising (a) a fuel; (b) a compound characterized by Formula I; and(c) a heavy compound, wherein the heavy compound comprises a compound ofFormula I having at least one atom replaced with an isotope tag.Generally, an isotope tag refers to an isotope of a particular atom thatreplaced such particular atom in a molecule, as will be described inmore detail later herein.

In an embodiment, a method of determining adulteration of a fuel furthercomprises (i) acquiring a fuel sample; (ii) adding a known amount of theheavy compound to the fuel sample to yield a marked fuel mixture; (iii)subjecting the marked fuel mixture to the analytical technique to recordan analytical signal for the compound characterized by Formula I and ananalytical signal for the heavy compound; (iv) comparing the analyticalsignal for the known amount of heavy compound to the analytical signalfor the compound characterized by Formula I; (v) determining a ratio ofan amount of the compound characterized by Formula I to the known amountof the heavy compound in the marked fuel mixture; and (vi) calculatingthe amount of the compound characterized by Formula I in the marked fuelmixture. As will be appreciated by one of skill in the art, and with thehelp of this disclosure, “amount” can refer to any suitable ways ofexpressing how much compound (e.g., fuel marker, heavy compound, etc.)is present in a composition (e.g., marked fuel composition, marked fuelmixture, etc.), such as for example concentration, molarity, molality,percent composition, mole fraction, weight fraction, parts per million(ppm), parts per billion (ppb), etc. For purposes of the disclosureherein, ppb and ppm are expressed as mass/mass (m/m), unless otherwisespecified.

In an embodiment, a method of determining adulteration of a fuelcomprises (i) contacting a fuel sample with a heavy compound to form amarked fuel mixture, wherein the fuel sample comprises a fuel and acompound characterized by Formula I, and wherein the heavy compoundcomprises the compound of Formula I having at least one atom replacedwith an isotope tag; (ii) subjecting the marked fuel mixture to solidphase extraction (SPE) to yield a marked fuel mixture fraction, whereinat least a portion of the compound characterized by Formula I and atleast a portion of the heavy compound elute together in the marked fuelmixture fraction; and (iii) subjecting to an analytical technique themarked fuel mixture fraction to determine fuel adulteration. In such anembodiment, the analytical technique comprises GC-MS using electronionization, wherein the compound characterized by Formula I can produceat least one ion having a mass-to-charge ratio of from about 300 toabout 600 at an ionization energy of equal to or greater than about 70eV.

While the present disclosure will be discussed in detail in the contextof a method of determining adulteration of a fuel, it should beunderstood that such method or any steps thereof can be applied in amethod of authenticating any other suitable liquid mixture. The liquidmixture can comprise any liquid mixture compatible with the disclosedmethods and materials. As used herein, “authenticating” of a fuel or anyother suitable liquid mixture refers to determining whether the fuel orany other suitable liquid mixture has been adulterated. Authenticatingof a fuel or any other suitable liquid mixture can comprise detectingthe presence and amount (e.g., concentration) of markers (e.g., fuelmarkers) in the fuel or any other suitable liquid mixture, as will bedescribed in more detail later herein.

In an embodiment, the marked fuel composition can comprise a fuel.Generally, a fuel is a material or substance that stores potentialenergy that can be released as useful energy (e.g., heat or thermalenergy, mechanical energy, kinetic energy, etc.) when the materialundergoes a chemical reaction (e.g., combustion).

In an embodiment, the fuel comprises a naturally-occurring material.Alternatively, the fuel comprises a synthetic material. Alternatively,the fuel comprises a mixture of a naturally-occurring and a syntheticmaterial. Nonlimiting examples of fuels suitable for use in the presentdisclosure include gasoline, diesel, jet fuel, kerosene, non-petroleumderived fuels, alcohol fuels, ethanol, methanol, propanol, butanol,biodiesel, maritime fuels, and the like, or combinations thereof.

In an embodiment, the marked fuel composition can comprise a fuelmarker. In an embodiment, the fuel maker can comprise at least onecompound characterized by Formula I:

wherein X can be carbon (C), oxygen (O), or sulfur (S); R¹ and R² caneach independently be hydrogen, a C₁ to C₂₀ alkyl group, or a C₆ to C₁₀aryl group; R³ and R^(3′) can each independently be hydrogen or a C₁ toC₄ alkyl group; R⁴ and R^(4′) can each independently be hydrogen, a C₁to C₄ alkyl group, a C₄ to C₁₀ cycloalkyl group, or a C₆ to C₁₀ arylgroup; R⁵ and R^(5′) can each independently be a C₄ to C₁₀ alkyl group;R⁶ and R^(6′) can each independently be hydrogen or a C₁ to C₆ alkylgroup; and R⁷ and R^(7′) can each independently be hydrogen or a C₁ toC₄ alkyl group. The compound characterized by Formula I can be furthersubjected to GC-MS using electron ionization, wherein the compoundcharacterized by Formula I produces at least one ion having amass-to-charge ratio of from about 300 to about 600 at an ionizationenergy of equal to or greater than about 70 eV, as will be described inmore detail later herein. In an embodiment, the marked fuel compositioncan comprise at least two compounds characterized by Formula I.

In an embodiment of the compound characterized by Formula I, X is O orS. In such an embodiment, R¹ and R² can be lone non-bonding electronpairs. Generally, a lone non-bonding electron pair is a pair ofelectrons (e.g., a valence set of two electrons) that is not bonding orshared with another atom—as opposed to bonding electron pairs that areshared between different atoms, as they form bonds (e.g., covalentbonds) between such atoms.

In an embodiment of the compound characterized by Formula I, X is O. Insuch an embodiment, the compound characterized by Formula I can haveStructure A:

In an embodiment of the compound characterized by Formula I, X is S. Insuch an embodiment, the compound characterized by Formula I can have anyof Structure B, Structure C, Structure D, Structure E, or Structure F:

In an embodiment of the compound characterized by Formula I, X is C. Insuch an embodiment, R¹ and R² can each independently be hydrogen, a C₁to C₂₀ alkyl group, or a C₆ to C₁₀ aryl group.

In an embodiment of the compound characterized by Formula I, X is C, andR¹ and R² can each independently be a C₁ to C₂₀ alkyl group,alternatively a C₁ to C₁₀ alkyl group, alternatively a C₁ to C₇ alkylgroup, or alternatively a C₁ to C₄ alkyl group. As used herein, the term“alkyl group” is a general term that refers to any univalent groupderived from an alkane by removal of a hydrogen atom from any carbonatom of the alkane. Further, as used herein, the term “alkyl groups” canrefer to primary alkyl groups, secondary alkyl groups (sec-alkylgroups), or tertiary alkyl groups (tert-alkyl groups or t-alkyl groups).Alkanes are acyclic branched or unbranched hydrocarbons having thegeneral formula C_(n)H_(2n+2) and consist entirely of hydrogen atoms andsaturated carbon atoms. For purposes of the disclosure herein, the term“alkyl group” refers to any alkyl group, including without limitationprimary alkyl groups, sec-alkyl groups, tert-alkyl groups, n-alkylgroups, iso-alkyl groups, substituted alkyl groups, unsubstituted ornon-substituted alkyl groups, and the like, or combinations thereof. Forexample, the term “butyl group” refers to a n-butyl group, an iso-butylgroup, a sec-butyl group, a tert-butyl group, or combinations thereof.Generally, a “substituted organic group” (e.g., substituted alkyl group,substituted cycloalkyl group, substituted aryl group, etc.) refers to anorganic group wherein a hydrogen atom has been substituted with an atomor group of atoms, e.g., a substituent. For purposes of the disclosureherein, a C_(x) to C_(y) organic group (e.g., an alkyl group, acycloalkyl group, an aryl group, etc.) includes groups represented byall integers between x and y, including x and y. For example, a C₁ toC₁₀ organic group includes C₁, C₂, C₃, C₄, C₅, C₆, C₇, C₈, C₉, and C₁₀organic groups. Further, for example, a C₆ to C₁₂ organic group includesC₆, C₇, C₈, C₉, C₁₀, C₁₁ and C₁₂ organic groups.

In an embodiment of the compound characterized by Formula I, X is C, andR¹ and R² can each independently be selected from the group consistingof a methyl group, an ethyl group, a n-propyl group, an iso-propylgroup, a n-butyl group, an iso-butyl group, a sec-butyl group, atert-butyl group, a pentyl group, a n-pentyl group, an iso-pentyl group,a sec-pentyl group, a hexyl group, a heptyl group, an octyl group, anonyl group, a decyl group, a undecyl group, a dodecyl group, a tridecylgroup, a tetradecyl group, a pentadecyl group, a hexadecyl group, aheptadecyl group, an octadecyl group and a nonadecyl group.

In an embodiment of the compound characterized by Formula I, X is C, andR¹ and R² can each independently be selected from the group consistingof a methyl group, an ethyl group, a n-propyl group, an iso-propylgroup, a n-butyl group, an iso-butyl group, a sec-butyl group, atert-butyl group and a heptyl group.

In an embodiment of the compound characterized by Formula I, X is C, andR¹ and R² can each be a methyl group.

In an embodiment of the compound characterized by Formula I, X is C, andR¹ and R² can each independently be a C₆ to C₁₀ aryl group,alternatively a C₆ to C₈ aryl group, alternatively a C₆ aryl group,alternatively a C₇ aryl group, or alternatively a C₈ aryl group. As usedherein, the term “aryl group” is a general term that refers to anyaromatic group derived from an arene by removal of a hydrogen atom fromany carbon atom of an aromatic ring. Generally, arenes (or aromatichydrocarbons) are hydrocarbons with alternating double bonds and singlebonds between carbon atoms, wherein the carbon atoms form rings, and canbe monocyclic arenes (e.g., benzene, toluene, o-xylene, m-xylene,p-xylene, biphenyl, diphenylmethane, etc.), which can contain one ormore aromatic rings, wherein the rings are not fused to each other; orpolycyclic arenes (e.g., naphthalene, anthracene, etc.), which cancontain two or more aromatic rings, wherein at least two of the ringsare fused to each other. Except for phenyl, which is derived by removalof a hydrogen atom from a carbon atom of a benzene ring, all other arylgroups are position dependent, with respect to the already existingsubstituents on the aromatic ring from which the hydrogen is removed tocreate such aryl group. For example, a tolyl group can be obtained byremoving one hydrogen atom from a carbon atom of the aromatic ring oftoluene, wherein such tolyl group can be o-tolyl, m-tolyl, or p-tolyl,based on whether the hydrogen was removed from a carbon that waspositioned in ortho, metha, or para, respectively, with respect to themethyl group. For purposes of the disclosure herein, the term “arylgroup” refers to any aryl group, including without limitation anyisomers, such as ortho, meta, para isomers, a substituted aryl group, aunsubstituted aryl group, and the like, or combinations thereof. Forexample, the term “tolyl group” refers to o-tolyl group, m-tolyl group,p-tolyl group, or combinations thereof.

In an embodiment of the compound characterized by Formula I, X is C, andR¹ and R² can each independently be hydrogen, a C₁ to C₁₀ alkyl group,or a C₆ to C₁₀ aryl group, wherein the C₆ to C₁₀ aryl group can comprisea phenyl group, a substituted phenyl group, a tolyl group, a substitutedtolyl group, a xylyl group, or a substituted xylyl group.

In an embodiment of the compound characterized by Formula I, X is C. Insuch an embodiment, the compound characterized by Formula I can have anyof Structures G-O:

In an embodiment of the compound characterized by Formula I, X is C, andR¹ and R² can each independently be a C₁ to C₄ alkyl group, or a C₆ toC₁₀ aryl group; wherein the C₆ to C₁₀ aryl group can comprise a phenylgroup, a substituted phenyl group, a tolyl group, a substituted tolylgroup, a xylyl group, or a substituted xylyl group.

In an embodiment of the compound characterized by Formula I, X is C, andR¹ and R² can each independently be selected from the group consistingof a methyl group, an ethyl group, a n-propyl group, an iso-propylgroup, a n-butyl group, an iso-butyl group, a sec-butyl group, atert-butyl group, a pentyl group, a n-pentyl group, an iso-pentyl group,a sec-pentyl group, a hexyl group, a heptyl group, an octyl group, anonyl group, a decyl group, a undecyl group, a dodecyl group, a tridecylgroup, a tetradecyl group, a pentadecyl group, a hexadecyl group, aheptadecyl group, an octadecyl group and a nonadecyl group. In such anembodiment, the compound characterized by Formula I can have any ofStructure G, Structure H, Structure I, Structure J, Structure K,Structure L, Structure M, Structure N, or Structure O.

In an embodiment of the compound characterized by Formula I, X is C. Insuch an embodiment, the compound characterized by Formula I can haveStructure P:

In an embodiment of the compound characterized by Formula I, X is C, andR¹ and R² can each independently be a methyl group or a phenyl group. Insuch an embodiment, the compound characterized by Formula I can haveStructure P.

In an embodiment of the compound characterized by Formula I, X is C, andR¹ and R² can each independently be hydrogen, a C₁ to C₁₀ alkyl group,or a C₆ to C₁₀ aryl group.

In an embodiment of the compound characterized by Formula I, X is C, andR¹ and R² can each independently be a C₁ to C₁₀ alkyl group, or a C₆ toC₁₀ aryl group. In such an embodiment, the compound characterized byFormula I can have Structure P.

In an embodiment, R³ and R^(3′) can each independently be hydrogen or aC₁ to C₄ alkyl group, such as for example a methyl group, an ethylgroup, a n-propyl group, an iso-propyl group, a n-butyl group, aniso-butyl group, a sec-butyl group, or a tert-butyl group.

In an embodiment, R³ and R^(3′) can each independently be hydrogen or amethyl group.

In an embodiment of the compound characterized by Formula I, X is O, andR³ and R^(3′) can each be hydrogen. In such an embodiment, the compoundcharacterized by Formula I can have Structure A.

In another embodiment of the compound characterized by Formula I, X isS, and R³ and R^(3′) can each be hydrogen. In such an embodiment, thecompound characterized by Formula I can have any of Structure B,Structure C, or Structure D.

In yet another embodiment of the compound characterized by Formula I, Xis C, and R³ and R^(3′) can each be hydrogen. In such an embodiment, thecompound characterized by Formula I can have any of Structure G,Structure H, Structure I, Structure J, Structure L, Structure M,Structure N, Structure O, or Structure P.

In still yet another embodiment of the compound characterized by FormulaI, X is S, and R³ and R^(3′) can each be a methyl group. In such anembodiment, the compound characterized by Formula I can have StructureE.

In still yet another embodiment of the compound characterized by FormulaI, X is S, and R³ and R^(3′) can each independently be hydrogen or amethyl group. In such an embodiment, the compound characterized byFormula I can have Structure F.

In still yet another embodiment of the compound characterized by FormulaI, X is C, and R³ and R^(3′) can each be a methyl group. In such anembodiment, the compound characterized by Formula I can have StructureK.

In an embodiment, R⁴ and R^(4′) can each independently be hydrogen, a C₁to C₄ alkyl group, a C₄ to C₁₀ cycloalkyl group, or a C₆ to C₁₀ arylgroup. As used herein, the term “cycloalkyl group” is a general termthat refers to any univalent group derived from a cycloalkane by removalof a hydrogen atom from any carbon atom of the cycloalkane ring.Cycloalkanes are saturated monocyclic hydrocarbons, and can be with orwithout side chains. Cycloalkanes and their corresponding cycloalkylgroups can also be substituted or unsubstituted. Whether the cycloalkylis substituted or unsubstituted, the nomenclature of the cycloalkylrefers to the number of carbon atoms present in the cycloalkane ring.For example, a cyclobutyl group has 4 carbon atoms in the cycloalkylring; and a methylcyclopropyl group has 3 carbon atoms in the cycloalkylring, but a total of 4 carbon atoms.

In an embodiment of the compound characterized by Formula I, X is O, andR⁴ and R^(4′) can each be hydrogen. In such an embodiment, the compoundcharacterized by Formula I can have Structure A.

In another embodiment of the compound characterized by Formula I, X isS, and R⁴ and R^(4′) can each be hydrogen. In such an embodiment, thecompound characterized by Formula I can have any of Structure B, orStructure E.

In yet another embodiment of the compound characterized by Formula I, Xis S, and R⁴ and R^(4′) can each independently be hydrogen or atert-butyl group. In such an embodiment, the compound characterized byFormula I can have Structure F.

In still yet another embodiment of the compound characterized by FormulaI, X is C, and R⁴ and R^(4′) can each be hydrogen. In such anembodiment, the compound characterized by Formula I can have any ofStructure I, Structure J, Structure K, Structure M, Structure O, orStructure P.

In an embodiment, R⁴ and R^(4′) can each independently be a C₁ to C₄alkyl group, such as for example a methyl group, an ethyl group, an-propyl group, an iso-propyl group, a n-butyl group, an iso-butylgroup, a sec-butyl group, or a tert-butyl group.

In an embodiment of the compound characterized by Formula I, X is S, andR⁴ and R^(4′) can each be a methyl group. In such an embodiment, thecompound characterized by Formula I can have any of Structure C, orStructure D.

In another embodiment of the compound characterized by Formula I, X isC, and R⁴ and R^(4′) can each be a methyl group. In such an embodiment,the compound characterized by Formula I can have any of Structure H, orStructure N.

In an embodiment, R⁴ and R^(4′) can each independently be a C₄ to C₁₀cycloalkyl group, such as for example a cyclobutyl group, a substitutedcyclobutyl group, a cyclopentyl group, a substituted cyclopentyl group,a cyclohexyl group, a substituted cyclohexyl group, a cycloheptyl group,a substituted cycloheptyl group, a cyclooctyl group, or a substitutedcyclooctyl group. In such an embodiment, the C₄ to C₁₀ cycloalkyl groupcan comprise a cyclohexyl group.

In an embodiment of the compound characterized by Formula I, X is C, andR⁴ and R^(4′) can each be a cyclohexyl group. In such an embodiment, thecompound characterized by Formula I can have Structure L.

In an embodiment, R⁴ and R^(4′) can each independently be a C₆ to C₁₀aryl group, such as for example a phenyl group, a substituted phenylgroup, a tolyl group, a substituted tolyl group, a xylyl group, or asubstituted xylyl group.

In an embodiment of the compound characterized by Formula I, X is C, andR⁴ and R^(4′) can each be a phenyl group. In such an embodiment, thecompound characterized by Formula I can have Structure G.

In an embodiment, R⁵ and R^(5′) can each independently be a C₄ to C₁₀alkyl group, such as for example a n-butyl group, an iso-butyl group, asec-butyl group, a tert-butyl group, a pentyl group, a n-pentyl group,an iso-pentyl group, a sec-pentyl group, a hexyl group, a heptyl group,an octyl group, a nonyl group, or a decyl group.

In an embodiment, R⁵ and R^(5′) can both be a pentyl group or a heptylgroup.

In an embodiment of the compound characterized by Formula I, X is S, andR⁵ and R^(5′) can each be a pentyl group. In such an embodiment, thecompound characterized by Formula I can have any of Structure D,Structure E, or Structure F.

In another embodiment of the compound characterized by Formula I, X isC, and R⁵ and R^(5′) can each be a pentyl group. In such an embodiment,the compound characterized by Formula I can have any of Structure G,Structure K, or Structure L.

In yet another embodiment of the compound characterized by Formula I, Xis O, and R⁵ and R^(5′) can each be a heptyl group. In such anembodiment, the compound characterized by Formula I can have StructureA.

In still yet another embodiment of the compound characterized by FormulaI, X is S, and R⁵ and R^(5′) can each be a heptyl group. In such anembodiment, the compound characterized by Formula I can have any ofStructure B, or Structure C.

In still yet another embodiment of the compound characterized by FormulaI, X is C, and R⁵ and R^(5′) can each be a heptyl group. In such anembodiment, the compound characterized by Formula I can have any ofStructure H, Structure I, Structure J, Structure M, Structure N,Structure O, or Structure P.

In an embodiment of the compound characterized by Formula I, X is C; R¹and R² can each be hydrogen; and R⁵ and R^(5′) can both be a C₄ to C₁₀alkyl group, such as for example a pentyl group or a heptyl group.

In an embodiment of the compound characterized by Formula I, X is C; R¹and R² can each be hydrogen; and R⁵ and R^(5′) can each be a pentylgroup. In another embodiment of the compound characterized by Formula I,X is C; R¹ and R² can each be hydrogen; and R⁵ and R^(5′) can each be aheptyl group.

In an embodiment of the compound characterized by Formula I, X is C; R¹and R² can each be a methyl group; and R⁵ and R^(5′) can both be a C₄ toC₁₀ alkyl group, such as for example a pentyl group or a heptyl group.

In an embodiment of the compound characterized by Formula I, X is C; R¹and R² can each be a methyl group; and R⁵ and R^(5′) can each be apentyl group. In such an embodiment, the compound characterized byFormula I can have any of Structure G, or Structure L.

In another embodiment of the compound characterized by Formula I, X isC; R¹ and R² can each be a methyl group; and R⁵ and R^(5′) can each be aheptyl group. In such an embodiment, the compound characterized byFormula I can have any of Structure H, Structure J, or Structure N.

In an embodiment, R⁴, R^(4′), R⁵, and R^(5′) can each independently be aC₁ to C₁₀ alkyl group, a C₄ to C₁₀ cycloalkyl group, or a C₆ to C₁₀ arylgroup, wherein the C₄ to C₁₀ cycloalkyl group can comprise a cyclobutylgroup, a substituted cyclobutyl group, a cyclopentyl group, asubstituted cyclopentyl group, a cyclohexyl group, a substitutedcyclohexyl group, a cycloheptyl group, a substituted cycloheptyl group,a cyclooctyl group, or a substituted cyclooctyl group. In such anembodiment, the C₄ to C₁₀ cycloalkyl group can comprise a cyclohexylgroup, such as for example in Structure L.

In an embodiment, R⁶ and R^(6′) can each independently be hydrogen or aC₁ to C₆ alkyl group, such as for example a methyl group, an ethylgroup, a n-propyl group, an iso-propyl group, a n-butyl group, aniso-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group,a n-pentyl group, an iso-pentyl group, a sec-pentyl group, or a hexylgroup.

In an embodiment, R⁶ and R^(6′) can each independently be selected fromthe group consisting of a methyl group, an ethyl group, a n-propylgroup, an iso-propyl group, a n-butyl group, an iso-butyl group, asec-butyl group, a tert-butyl group, a pentyl group, a n-pentyl group,an iso-pentyl group, a sec-pentyl group and a hexyl group.

In an embodiment of the compound characterized by Formula I, X is O, andR⁶ and R^(6′) can each be hydrogen. In such an embodiment, the compoundcharacterized by Formula I can have Structure A.

In another embodiment of the compound characterized by Formula I, X isS, and R⁶ and R^(6′) can each be hydrogen. In such an embodiment, thecompound characterized by Formula I can have any of Structure B, orStructure C.

In yet another embodiment of the compound characterized by Formula I, Xis S, and R⁶ and R^(6′) can each be a tert-butyl group. In such anembodiment, the compound characterized by Formula I can have any ofStructure D, or Structure E.

In still yet another embodiment of the compound characterized by FormulaI, X is S, and R⁶ and R^(6′) can each independently be hydrogen or atert-butyl group. In such an embodiment, the compound characterized byFormula I can have Structure F.

In still yet another embodiment of the compound characterized by FormulaI, X is C, and R⁶ and R^(6′) can each be hydrogen. In such anembodiment, the compound characterized by Formula I can have any ofStructure G, Structure I, Structure L, Structure M, Structure N,Structure O, or Structure P.

In still yet another embodiment of the compound characterized by FormulaI, X is C, and R⁶ and R^(6′) can each be methyl. In such an embodiment,the compound characterized by Formula I can have Structure H.

In still yet another embodiment of the compound characterized by FormulaI, X is C, and R⁶ and R^(6′) can each be iso-propyl. In such anembodiment, the compound characterized by Formula I can have StructureJ.

In still yet another embodiment of the compound characterized by FormulaI, X is C, and R⁶ and R^(6′) can each be a tert-butyl group. In such anembodiment, the compound characterized by Formula I can have StructureK.

In an embodiment, R⁷ and R^(7′) can each independently be hydrogen or aC₁ to C₄ alkyl group, such as for example a methyl group, an ethylgroup, a n-propyl group, an iso-propyl group, a n-butyl group, aniso-butyl group, a sec-butyl group, or a tert-butyl group.

In an embodiment, R⁷ and R^(7′) can each independently be hydrogen or amethyl group.

In an embodiment of the compound characterized by Formula I, X is O, andR⁷ and R^(7′) can each be hydrogen. In such an embodiment, the compoundcharacterized by Formula I can have Structure A.

In another embodiment of the compound characterized by Formula I, X isS, and R⁷ and R^(7′) can each be hydrogen. In such an embodiment, thecompound characterized by Formula I can have any of Structure B,Structure C, Structure D, or Structure E.

In yet another embodiment of the compound characterized by Formula I, Xis S, and R⁷ and R^(7′) can each independently be hydrogen or a methylgroup. In such an embodiment, the compound characterized by Formula Ican have Structure F.

In still yet another embodiment of the compound characterized by FormulaI, X is C, and R⁷ and R^(7′) can each be hydrogen. In such anembodiment, the compound characterized by Formula I can have any ofStructure G, Structure H, Structure I, Structure J, Structure K,Structure L, Structure M, Structure N, Structure O, or Structure P.

In an embodiment, the compound characterized by Formula I can beproduced by reaction of an intermediate phenol (AAA) with an alkylatingagent R⁵X to yield Formula I according to the following reaction:

Other alkylating agents, such as alcohol derivatives (mesylates,tosylates, etc.) can be employed. Intermediate phenols AAA can be madeby any suitable methodology. One example where X is C includes thereaction of a ketone with the appropriate phenol (BBB), according to thefollowing reaction scheme:

Subsequent alkylation as described leads to compounds of Formula I.

In an embodiment, a fuel marker comprising a compound characterized byFormula I as disclosed herein can be resistant to laundering. Generally,“laundering” of a fuel refers to processing or treating the fuel withlaundering agents to partially or completely remove or mask the fuelmarker such that the fuel cannot be properly authenticated. For purposesof the disclosure herein, the term “laundering agent” refers to anymaterial or substance which is capable of partially or completelyremoving a fuel marker from a marked fuel composition.

Nonlimiting examples of laundering agents include strong acids, alkalis,absorbent materials, clay, carbon, active carbon, charcoal, activecharcoal, paper filter, straw, microfilters, silica, silica gel,molecular sieves, adsorbent materials, and the like, or combinationsthereof.

In an embodiment, the fuel marker can be present within the marked fuelcomposition in an amount of from about 1 ppb to about 50 ppm,alternatively from about 10 ppb to about 25 ppm, alternatively fromabout 100 ppb to about 10 ppm, alternatively from about 250 ppb to about5 ppm, or alternatively from about 500 ppb to about 1 ppm, based on thetotal weight of the marked fuel composition.

In an embodiment, the marked fuel composition can be contacted with aheavy compound to yield a marked fuel mixture, wherein the heavycompound comprises a compound of Formula I having at least one atomreplaced with an isotope tag (e.g., a heavy compound of Formula I). Insuch an embodiment, the heavy compound can be contacted in a knownamount with the marked fuel composition, as will be disclosed in moredetail later herein. Generally, an isotope tag refers to an atom thatreplaced in a molecule (e.g., a molecule of a compound of Formula I)another atom of the same element that has a different number of neutronswhen compared to the atom that replaced it. For purposes of thedisclosure herein, a fuel composition comprising a heavy compound willbe referred to as a “marked fuel mixture,” or simply “marked fuelcomposition.”

Nonlimiting examples of isotope tags suitable for use in the presentdisclosure include deuterium (²H), carbon-13 (¹³C), oxygen-17 (¹⁷O),sulfur-34 (³⁴S), and the like, or combinations thereof. For example, acommercially available phenol-²H₆ (e.g., deuterated phenol d-BBB) can bereacted with ketones to create various deuterated bisphenol derivatives(e.g., d-AAA) according to the following reaction scheme:

Subsequent alkylation yields the desired heavy compounds (e.g.,deuterated compound of Formula I, d-Formula I). Performing the samesynthesis with a commercially available ¹³C₆ labelled phenol would yieldthe ¹³C heavy compound. One skilled in the art would recognize thatother isotopically labelled intermediates could be used to synthesize avariety of heavy compounds of various isotopic substitution.

In an embodiment, the marked fuel mixture comprises a heavy compound ofFormula I, wherein the isotope tag comprises deuterium (²H). In such anembodiment, the heavy compound of Formula I can further comprise otherisotope tags, such as for example carbon-13 (¹³C), oxygen-17 (¹⁷O),sulfur-34 (³⁴S), and the like, or combinations thereof.

In an embodiment, the marked fuel mixture comprises a heavy compound ofFormula I, wherein the isotope tag comprises carbon-13 (¹³C). In such anembodiment, the heavy compound of Formula I can further comprise otherisotope tags, such as for example deuterium (²H), oxygen-17 (¹⁷O),sulfur-34 (³⁴S), and the like, or combinations thereof.

In an embodiment, the marked fuel mixture comprises a heavy compound ofFormula I, wherein the isotope tag comprises oxygen-17 (¹⁷O). In such anembodiment, the heavy compound of Formula I can further comprise otherisotope tags, such as for example deuterium (²H), carbon-13 (¹³C),sulfur-34 (³⁴S), and the like, or combinations thereof.

In an embodiment, the marked fuel mixture comprises a heavy compound ofFormula I, wherein X can be O, wherein X comprises the isotope tag, andwherein the isotope tag comprises oxygen-17 (¹⁷O). In such anembodiment, the heavy compound of Formula I can further comprise otherisotope tags, such as for example deuterium (²H), carbon-13 (¹³C),sulfur-34 (³⁴S), and the like, or combinations thereof.

In an embodiment, the marked fuel mixture comprises a heavy compound ofFormula I, wherein X can be S, and wherein the isotope tag comprisessulfur-34 (³⁴S). In such an embodiment, the heavy compound of Formula Ican further comprise other isotope tags, such as for example deuterium(²H), carbon-13 (¹³C), oxygen-17 (¹⁷O), and the like, or combinationsthereof.

In an embodiment, the isotope tag can be introduced into the compound ofFormula I to form a heavy compound by using any suitable methodology. Inan embodiment, the isotope tag can be introduced into the compound ofFormula I by chemical isotope exchange (i.e., exchange of isotopesbetween different types of molecules or ions in the course of a chemicalreaction).

In some embodiments, the isotope tag can be introduced into the compoundof Formula I by subjecting the compound of Formula I to a chemicalisotope exchange with at least one isotope tag compound. Generally, anisotope tag compound refers to any compound containing an isotope tag(e.g., deuterium (²H), carbon-13 (¹³C), oxygen-17 (¹⁷O), sulfur-34(³⁴S), etc.), where such isotope tag compound can participate in achemical isotope exchange reaction and/or a reaction for transferringthe isotope tag to another compound.

In other embodiments, the isotope tag can be introduced into thecompound of Formula I by subjecting a precursor of the compound ofFormula I to a chemical isotope exchange with at least one isotope tagcompound. For example, during the synthesis of the compound of FormulaI, a precursor of the compound of Formula I can be subjected to achemical isotope exchange with at least one isotope tag compound.

In yet other embodiments, the isotope tag can be introduced into thecompound of Formula I by subjecting a first precursor of the compound ofFormula I to a reaction with at least one isotope tag compound to yielda second precursor of the compound of Formula I, wherein the secondprecursor of the compound of Formula I comprises an isotope tag. In suchembodiments, the second precursor of the compound of Formula I can befurther converted to yield a heavy compound of Formula I, wherein theheavy compound of Formula I comprises an isotope tag.

In still yet other embodiments, the isotope tag can be introduced intothe compound of Formula I by subjecting a precursor of the compound ofFormula I to a reaction with at least one isotope tag compound to yielda heavy compound of Formula I, wherein the heavy compound of Formula Icomprises an isotope tag. In an embodiment, the isotope tag can belocated at any position in the structure, alternatively the structurecomprises isotope tags at multiple positions. In an embodiment, theposition for isotopic substitution can be chosen to lead to asignificant shift in the mass-to-charge ratio (m/z) of the heavycompound. For example, the position for isotopic substitution can bechosen to provide a m/z shift of from about 4 atomic mass units (AMU) toabout 12 AMU, alternatively greater than about 4 AMU, alternativelygreater than about 8 AMU, or alternatively greater than about 12 AMU.

In some embodiments, a precursor of the compound of Formula I (e.g., afirst precursor of the compound of Formula I, a second precursor of thecompound of Formula I, etc.) can comprise an isotope tag compound, suchas for example deuterated 1-bromopentane (1-bromopentane-d₁₁, CsD₁₁Br),deuterated 1-bromoheptane (1-bromoheptane-d₁₅, C₇D₁₅Br), deuteratedphenol (C₆D₅OD), and the like, or combinations thereof.

Nonlimiting examples of isotope tag compounds suitable for use in thepresent disclosure include deuterated 1-bromopentane(1-bromopentane-d₁₁, CsD₁₁Br), deuterated 1-bromoheptane(1-bromoheptane-d₁₅, C₇D₅Br), deuterated phenol (C₆D₅OD), deuteratedwater (deuterium oxide, D₂O), deuterated hydrochloric acid (DCl),deuterated acetic acid (CD₃COOD), deuterated acetone (CD₃COCD₃),deuterated methanol (CD₃OD), deuterated acetonitrile (CD₃CN), deuteratedbenzene (C₆D₆), deuterated chloroform (CDCl₃), deuterated cyclohexane(C₆D₁₂), deuterated N,N-dimethylformamide (DCON(CD₃)₂), deuterateddimethyl sulphoxide (CD₃SOCD₃), deuterated ethanol (C₂D₅OD), deuteratedmethylene chloride (CD₂Cl₂), deuterated nitromethane (CD₃NO₂),deuterated pyridine (C₅D₅N), deuterated tetrahydrofuran (C₄D₈O),deuterated toluene (C₆D₅CD₃), deuterated trifluoroacetic acid (CF₃COOD);acetaldehyde-1-¹³C, acetaldehyde-1,2-¹³C₂, acetic acid-1-¹³C, aceticacid-2-¹³C, acetic acid-1,2-¹³C, acetic anhydride-1,1-¹³C₂, aceticanhydride-2,2-¹³C₂, acetic anhydride-1,1,2,2-¹³C₄, acetone-2-¹³C,acetone-1,3-¹³C₂, acetone-1,2,3-¹³C₃, acetonitrile-1-¹³C,acetonitrile-2-¹³C, acetonitrile-1,2-¹³C₂, acetophenone-1-¹³C,acetophenone-2-¹³C, acetyl chloride-1-¹³C, acetyl chloride-2-¹³C, acetylchloride-1,2-¹³C₂, aniline-¹³C₆, aniline chloride-¹³C₆, anilinesulfate-¹³C₆, benzaldehyde-carbonyl-¹³C, benzene-¹³C₆, benzenesulfonylchloride-¹³C₆, benzoic acid-carbonyl-¹³C, benzophenone-¹³C (carbonyllabeled), benzophenone-¹³C₁₂ (ring labeled), benzoyl chloride-¹³C (ringlabeled), benzoyl chloride-carbonyl-¹³C, benzyl alcohol-¹³C₆ (ringlabeled), tert-butyl chloride-¹³C, carbon dioxide-¹³C, carbondisulfide-¹³C, carbon monoxide-¹³C, carbon tetrachloride-¹³C,chloroacetic acid-1-¹³C, chloroacetic acid-2-¹³C, chloroaceticacid-1,2-¹³C₂, chlorobenzene-¹³C₆, chloroethane-1,2-¹³C₂,chloroform-¹³C, chloromethane-¹³C, cyanoacetic acid-1-¹³C, cyanoaceticacid-2-¹³C, cyanoacetic acid-¹³C (cyanide labeled), dichloromethane-¹³C,dimethyl formamide-carbonyl-¹³C, dimethyl-¹³C₂ sulfoxide, ethylacetate-1-¹³C, ethyl acetate-2-¹³C, ethyl alcohol-1-¹³C, ethylalcohol-2-¹³C, ethyl alcohol-1,2-¹³C₂, ethylamine-1-¹³C, ethylchloride-1,2-¹³C₂, ethylene oxide-1,2-¹³C₂, formaldehyde-¹³C,formamide-¹³C, hexane-1-¹³C, 1,6-hexanediamine-1,6-¹³C₂,isobutane-2-¹³C, isopropanol-2-¹³C, methane-¹³C, methyl alcohol-¹³C,methylamine-¹³C, methyl bromide-¹³C, methyl chloride-¹³C, methylenechloride-¹³C, methyl formate-¹³C, nitrobenzene-¹³C₆, nitromethane-¹³C,phosgene-¹³C, propane-2-¹³C, 1,3-propanediol-2-¹³C, propene-1-¹³C,propene-2-¹³C, propene-3-¹³C, sodium acetate-1-¹³C, sodiumacetate-2-¹³C, sodium acetate-1,2-¹³C₂, sodium bicarbonate-¹³C, sodiumcarbonate-¹³C, sodium cyanide-¹³C, sodium formate-¹³C, sodiumthiocyanate-¹³C, thiourea-¹³C, toluene-7-¹³C, trichloroaceticacid-1,2-¹³C₂₀, urea-¹³C; water-¹⁷O, acetaldehyde-¹⁷O, adipic acid-¹⁷O₄,ammonium nitrate-¹⁷O₃, benzophenone-¹⁷O, carbon dioxide-¹⁷O₂, carbonmonoxide-¹⁷O, carbonyl sulfide-¹⁷O, cyclopentanone-¹⁷O, deuteriumoxide-¹⁷O, dimethyl formamide-¹⁷O, ethanol-¹⁷O, formic acid-¹⁷O, nitrousoxide-¹⁷O, oxygen-¹⁷O₂, phosgene-¹⁷O, urea-¹⁷O; carbon disulfide-³⁴S,carbonyl sulfide-³⁴S, magnesium sulfate-³⁴S, potassium thiocyanate-³⁴S,sulfur-³⁴S, sodium sulfate-³⁴S, sulfur dioxide-³⁴S, sulfuric acid-³⁴S,thioacetamide-³⁴S, thioacetic acid-³⁴S, thiourea-³⁴S; deuterated aceticacid-1-¹³C (CD₃CO₂D), deuterated acetic acid-2-¹³C (CD₃CO₂D), deuteratedacetone-1,3-¹³C₂ (CD₃COCD₃), deuterated acetone-1,2,3-¹²C₃(CD₃COCD₃),deuterated acetonitrile-1,2-¹²C (CD₃CN), deuterated acetonitrile-¹⁵N(CD₃CN), deuterated acetonitrile-1-¹³C (CD₃CN), deuterated ammonia-¹⁵N(ND₃), deuterated ammonium chloride-¹⁵N (ND₄Cl), deuterated ammoniumsulfate-¹⁵N₂ ((ND₄)₂SO₄), deuterated methane-¹³C (CH₃D), deuteratedmethane-¹³C (CD₄), deuterated methyl alcohol-¹³C (CD₃OD), deuteratedsodium acetate-1-¹³C (CD₃CO₂Na), deuterated sodium acetate-2-¹³C(CD₃CO₂Na), deuterated urea-¹³C (ND₂COND₂), deuterated urea-¹³C,¹⁵N₂(ND₂COND₂); carbon dioxide-¹³C,¹⁷O; cyanamide-¹³C,¹⁵N₂;formamide-¹³C,¹⁵N; thiourea-¹³C,¹⁵N₂; urea-¹³C,¹⁵N₂; and the like, orcombinations thereof.

In some embodiments, the isotope tag compounds can comprise deuterated1-bromopentane (1-bromopentane-d₁₁, CsD₁₁Br). In other embodiments, theisotope tag compounds can comprise deuterated 1-bromoheptane(1-bromoheptane-d₁₅, C₇D₁₅Br). In yet other embodiments, the isotope tagcompounds can comprise deuterated phenol (C₆D₅OD).

As will be appreciated by one of skill in the art, and with the help ofthis disclosure, more than one isotope tag can be introduced into achemical compound, such as for example 2, 3, 4, 5, 6, 7, 8, 9, 10, ormore isotope tags. In some embodiments, at least two of the isotope tagsof the compound of Formula I are the same. In other embodiments, atleast two of the isotope tags of the compound of Formula I aredifferent. In yet other embodiments, at least two of the isotope tags ofthe compound of Formula I can be the same, and/or at least two of theisotope tags of the compound of Formula I can be different.

In an embodiment of a heavy compound of Formula I (e.g., deuteratedcompound of Formula I, d-Formula I), X is S. In such an embodiment, theheavy compound of Formula I can have any of deuterated Structure B(d-Structure B), or deuterated Structure F (d-Structure F):

In an embodiment, the heavy compound can be present within the markedfuel mixture in an amount (e.g., can be added to a fuel composition in aknown amount) of from about 1 ppb to about 50 ppm, alternatively fromabout 10 ppb to about 25 ppm, alternatively from about 100 ppb to about10 ppm, alternatively from about 250 ppb to about 5 ppm, oralternatively from about 500 ppb to about 1 ppm, based on the totalweight of the marked fuel mixture.

In an embodiment, the marked fuel composition can be prepared by usingany suitable methodology. In an embodiment, a method of forming a markedfuel composition can comprise contacting (a) a fuel, and (b) a fuelmarker comprising at least one compound characterized by Formula I.

In some embodiments, the fuel marker comprising at least one compoundcharacterized by Formula I can be added to the fuel to form the markedfuel composition. In other embodiments, the fuel can be added to thefuel marker comprising at least one compound characterized by Formula Ito form the marked fuel composition.

In some embodiments, the fuel marker can be contacted with the fuel inpowder form. In other embodiments, the fuel marker can be contacted withthe fuel as a fuel marker solution, wherein the fuel marker can besolubilized in one or more solvents to form a fuel marker solution. Inan embodiment, a solvent suitable for use in the present disclosure ischaracterized by a flash point greater than about 60° C. and miscibilitywith the fuels disclosed herein. Nonlimiting examples of solventssuitable for use in the present disclosure for making a fuel markersolution include hydrocarbons, aromatic hydrocarbons, halogenatedhydrocarbons, ethers, carbonates, esters, ketones, aldehydes, alcohols,nitriles, and combinations thereof. Polar solvents which can be utilizedinclude without limitation water, ethers, carbonates, esters, ketones,aldehydes, alcohols, nitriles, and mixtures thereof; alternatively,ethers, carbonates, esters, ketones, aldehydes, alcohols, nitriles, andmixtures thereof. Aprotic polar solvents which can be utilized includewithout limitation ethers, esters, ketones, aldehydes, nitriles, andmixtures thereof; alternatively, ethers, nitriles, and mixtures thereof.Non-polar solvents include without limitation hydrocarbons, aromatichydrocarbons, halogenated hydrocarbons, or mixtures thereof;alternatively, a hydrocarbon; alternatively, an aromatic hydrocarbon; oralternatively, a halogenated hydrocarbon. In another embodiment, thesolvent comprises aromatic solvent 150 and 200, N-methylpyrollidone,2-ethylhexanol, hydrocarbon solvents such as mineral spirits, and thelike, or combinations thereof.

In an embodiment, an additive pack can comprise the fuel marker. In suchan embodiment, the additive pack comprises a fuel marker solution. In anembodiment, the additive pack can further comprise a detergent, asurfactant, a lubricant, an octane enhancer, a crystallizationinhibitor, a freeze point depressant, and the like, or combinationsthereof. In an embodiment, the additive pack comprising the fuel markercan be contacted with the fuel to form a marked fuel composition.

In embodiments where an additive pack is used, the fuel markercomprising a compound characterized by Formula I can be mixed with theadditive pack prior to adding the additive pack to the fuel. In analternative embodiment, where the additive pack is used, the fuel markercomprising the compound characterized by Formula I and the additive packcan be added to the fuel at the same time, without prior mixing of thefuel marker with the additive pack. In other embodiments, where theadditive pack is used, the additive pack and the fuel marker comprisingthe compound characterized by Formula I can be added to the fuel atdifferent times. For example, the additive pack can be added to the fuelfirst, and the fuel marker comprising the compound characterized byFormula I can be added to the fuel second. Further, for example, thefuel marker comprising the compound characterized by Formula I can beadded to the fuel first, and the additive pack can be added to the fuelsecond.

As will be appreciated by one of skill in the art, and with the help ofthis disclosure, whether the fuel marker is contacted with the fuel inpowder form, as a fuel marker solution, or as part of an additive pack,the concentration of the fuel marker in the marked fuel composition canbe known (e.g., calculated) based on the amount of powder used, theconcentration of the fuel marker in the fuel marker solution or theadditive pack, the amount of fuel marker solution or additive pack used,etc.

In an embodiment, the fuel can be contained in a container, a storagecontainer, transport container, a tanker truck, tanker ship, pipeline,or any other suitable means for transporting fuel from one place toanother.

In an embodiment, the fuel can be in a pipeline. For example, the fuelcould be transported through the pipeline from a processing plant to astorage container. In such an embodiment, the fuel marker can beinjected through an injection valve into a fuel stream travellingthrough the pipeline.

In an embodiment, the fuel can be in a transport container (e.g., tankertruck, a tanker ship, etc.). In such an embodiment, the fuel marker canbe added to the transport container through a port located on thetransport container above the level of the fuel in the container.Further, the fuel marker can be injected through an injection valve intothe transport container, wherein the injection valve can be locatedbelow the level of the fuel in the container.

In an embodiment, the storage container comprising the fuel can be astatic storage container (e.g., the storage container is immobile, doesnot move or travel), wherein the static storage container could belocated above ground, below ground, or partially below ground andpartially above ground. In such an embodiment, the fuel marker can beadded to the static storage container through a port located on thestatic storage container above the level of the fuel in the container.Further, the fuel marker can be injected through an injection valve intothe static storage container, wherein the injection valve can be locatedbelow the level of the fuel in the container.

In an embodiment, the storage container comprising the fuel can be amobile storage container (e.g., the storage container is mobile, it canmove or travel). In such an embodiment, the fuel marker can be added tothe mobile storage container through a port located on the mobilestorage container above the level of the fuel in the container. Further,the fuel marker can be injected through an injection valve into themobile storage container, wherein the injection valve can be locatedbelow the level of the fuel in the container.

In some embodiments, the fuel marker can be added to a dry container(e.g., a container comprising no fuel). In such embodiments, the fuelcan be added to the container subsequent to the addition of the fuelmarker to the container.

In an embodiment, a method of determining (e.g., evaluating, assessing,estimating, etc.) adulteration of a fuel can comprise subjecting to ananalytical technique a marked fuel composition comprising a fuel and afuel marker, wherein the fuel marker comprises a compound characterizedby Formula I.

In an embodiment, the analytical technique can comprise GC-MS, nuclearmagnetic resonance (NMR) spectroscopy, ¹³C NMR spectroscopy, surfaceenhanced Raman scattering spectroscopy, and the like, or combinationsthereof.

In an embodiment, a method of determining adulteration of a fuel cancomprise (i) acquiring a fuel sample; (ii) subjecting the fuel sample tothe analytical technique to determine fuel sample data (e.g., markerconcentration); and (iii) comparing the fuel sample data to a targetmarking level (e.g., target marker concentration; control data) used tomark the fuel. As will be appreciated by one of skill in the art, andwith the help of this disclosure, the target marker concentration of themarked fuel composition is generally acquired for marked fuelcompositions at a point where the fuel sample data is known, e.g., priorto any possibility of adulteration. For example, acquisition of thetarget marker concentration at the place of marking as quality standardcan provide for dosing of the marked fuels at the target marking level.

In some embodiments, a method of determining adulteration of a fuel canbe performed without addition of standards to the fuel sample. In anembodiment, a method of determining adulteration of a fuel excludes theaddition of standards to the fuel sample.

In other embodiments, a method of determining adulteration of a fuel canrequire addition of a standard (e.g., internal standard) to the fuelsample, such as for example a heavy compound, as will be described inmore detail later herein.

In an embodiment, if the fuel sample data (e.g., marker concentration)matches the control data of the marked fuel composition (e.g., targetmarker concentration), the fuel can be deemed to be unadulterated fuel.As will be appreciated by one of skill in the art, and with the help ofthis disclosure, the “matching” of the fuel sample data (e.g., markerconcentration) with the control data of the marked fuel composition(e.g., target marker concentration) has to be within experimental errorlimits for the fuel sample to be deemed unadulterated, and suchexperimental error limits are dependent on the particular analyticaltechnique used, the analytical instrumentation used for the detectionand analysis of the fuel marker, etc. The matching of data could includemeasuring a marker concentration to determine if the fuel has beendiluted, by comparing the marker concentration with the target markerconcentration. The matching of data could also include the detection ofa marker that has been added to a potential adulterant and should not bepresent in the fuel. Quantification of the amount of such a marker wouldindicate the extent of dilution by the potential adulterant.

In an embodiment, if the fuel sample data does not match the controldata of the marked fuel composition, the fuel can be deemed to beadulterated fuel. As will be appreciated by one of skill in the art, andwith the help of this disclosure, the difference between the fuel sampledata and the control data of the marked fuel composition has to falloutside of experimental error limits (e.g., the fuel sample data and thecontrol data of the marked fuel composition do not match) for the sampleto be deemed adulterated, and such experimental error limits aredependent on the particular analytical technique used, the analyticalinstrumentation used for the detection and analysis of the fuel marker,etc. Methods for matching and determination of the extent ofadulteration of a marked fuel, as well as methods for fuelauthentication by using more than one marker, are disclosed in greaterdetail in U.S. Pat. No. 8,592,213, which is incorporated by referenceherein in its entirety.

In an embodiment, a method of determining adulteration of a fuel can beperformed in the field (e.g., on location, direct detection, etc.).Determining adulteration of a fuel in the field can include testing atany location where a fuel can be found. Determining adulteration in thefield can allow for rapid qualitative and/or quantitative assessment ofthe presence and/or amount of fuel marker in a fuel sample.

In another embodiment, a fuel sample can be collected from a firstlocation (e.g., a gas station), and then transported to a secondlocation (e.g., a laboratory) for further testing, e.g., determiningadulteration.

In an embodiment, a method of determining adulteration of a fuel cancomprise contacting a marked fuel composition with a heavy compound toyield a marked fuel mixture, wherein the heavy compound comprises acompound of Formula I having at least one atom replaced with an isotopetag. In such an embodiment, a known amount of the heavy compound can becontacted with (e.g., added to) the marked fuel composition to yield themarked fuel mixture (e.g., wherein the heavy compound can be present inthe marked fuel mixture in a known amount). The heavy compound can beused as an internal standard.

In an embodiment, the method of determining adulteration of a fuel canfurther comprise subjecting the marked fuel mixture to an analyticaltechnique.

In an embodiment, the analytical technique can evaluate fueladulteration by (i) determining the presence of the heavy compound inthe marked fuel mixture; and (ii) determining a ratio of an amount ofthe compound characterized by Formula I to the known amount of the heavycompound in the marked fuel mixture.

In an embodiment, (i) determining the presence of the heavy compound inthe marked fuel mixture can further comprise determining the presence ofthe compound characterized by Formula I in the marked fuel mixture.

In an embodiment, (ii) determining a ratio of an amount of the compoundcharacterized by Formula I to a known amount of the heavy compound inthe marked fuel mixture further comprises calculating the amount of thecompound characterized by Formula I in the marked fuel mixture.

As will be appreciated by one of skill in the art, and with the help ofthis disclosure, the compound characterized by Formula I and the heavycompound comprising a compound of Formula I having at least one atomreplaced with an isotope tag can have the same chemical and physicalproperties, such as for example, melting temperature, solubility,density, absorption, reactivity, chemical stability, elution time, etc.Further, as will be appreciated by one of skill in the art, and with thehelp of this disclosure, when present in the same composition (e.g.,marked fuel mixture), the compound characterized by Formula I and theheavy compound comprising a compound of Formula I having at least oneatom replaced with an isotope tag are challenging to separate from eachother by conventional analytical methods, such as chromatography, andwill be analyzed simultaneously, or nearly simultaneously by theanalytical technique.

In an embodiment, the compound characterized by Formula I and the heavycompound comprising a compound of Formula I having at least one atomreplaced with an isotope tag can each display analytical signals thatare different (e.g., distinct, dissimilar, etc.) from each other,thereby enabling simultaneous detection of both the compoundcharacterized by Formula I and the heavy compound. As will beappreciated by one of skill in the art, and with the help of thisdisclosure, isotope tags have unique analytical signals and can bedetected by a variety of analytical techniques, and such uniqueanalytical signals do not appear in the absence of the isotope tag.

In an embodiment, the marked fuel mixture can be subjected to theanalytical technique to record an analytical signal for the compoundcharacterized by Formula I and an analytical signal for the heavycompound in the marked fuel mixture. In such an embodiment, theanalytical signal for the compound characterized by Formula I and theanalytical signal for the heavy compound in the marked fuel mixture canbe different.

In some embodiments, the analytical signal for the compoundcharacterized by Formula I and the analytical signal for the heavycompound in the marked fuel mixture can correlate (e.g., beproportional, be directly proportional, etc.) with the amount of thecompound characterized by Formula I and the amount (e.g., known amount)of the heavy compound in the marked fuel mixture, respectively. In suchembodiments, a ratio of the analytical signal for the compoundcharacterized by Formula I to the analytical signal for the heavycompound in the marked fuel mixture can be the same as (e.g., equal to)the ratio of the amount of the compound characterized by Formula I tothe known amount of the heavy compound in the marked fuel mixture. Theratio of the amount of the compound characterized by Formula I to theknown amount of the heavy compound in the marked fuel mixture can beused for calculating the amount of the compound characterized by FormulaI in the marked fuel mixture based on the known amount of the heavycompound in the marked fuel mixture. As will be appreciated by one ofskill in the art, and with the help of this disclosure, the heavycompound is used as an internal standard for determining the amount ofthe compound characterized by Formula I in the marked fuel mixture. Theinternal standard is held fixed at a predetermined concentration thatwill be used in the analysis and the analyte (e.g., compoundcharacterized by Formula I) concentration is varied. The resulting datais used then to generate a calibration curve that can be utilized inquantitating the fuel sample data (e.g., fuel marker concentration).

The selection of an appropriate internal standard can be very importantin generating the most accurate results in this particular type ofanalysis (e.g., fuel authentication using a heavy compound as internalstandard). For GC-MS analysis, deuterated isotopologues can often be thebest choice if available, as they can very closely match a retentiontime of the fuel marker, and can produce a signal on a different masschannel of a MS detector, which would not interfere with integration ofthe fuel marker signal. Alternatively, a structural isomer of a fuelmarker structure can be used to produce similar results, or a closelyrelated structure in the same or very similar chemical class can beutilized. Without wishing to be limited by theory, the more structurallysimilar the internal standard is to the fuel marker structure, the moreaccurate the results will be.

In some embodiments, an internal standard can be co-submitted orco-injected (e.g., via an automated liquid injector) along with anunknown sample (e.g., fuel sample) for analysis (e.g., GC-MS analysis).In other embodiments, an internal standard solution can be mixed with anunknown solution (e.g., fuel sample to be authenticated) to form acombined solution, and the combined solution can be submitted orinjected for analysis (e.g., GC-MS analysis). As will be appreciated byone of skill in the art, and with the help of this disclosure, whetherthe internal standard and the fuel sample are pre-mixed or co-injected,similar results will be obtained from the GC-MS analysis.

In an embodiment, the method of determining adulteration of a fuel cancomprise determining an amount (e.g., concentration) of a fuel marker(e.g., a compound characterized by Formula I) in the fuel sample, basedon the fuel sample data (e.g., analytical signal).

In an embodiment, a method of determining adulteration of a fuel cancomprise (i) acquiring a fuel sample; (ii) adding a known amount of theheavy compound to the fuel sample to yield a marked fuel mixture; (iii)subjecting the marked fuel mixture to the analytical technique to recordan analytical signal for the compound characterized by Formula I and ananalytical signal for the heavy compound; (iv) comparing the analyticalsignal for the known amount of heavy compound to the analytical signalfor the compound characterized by Formula I; (v) determining a ratio ofan amount of the compound characterized by Formula I to the known amountof the heavy compound in the marked fuel mixture; and (vi) calculatingthe amount of the compound characterized by Formula I in the marked fuelmixture. In such an embodiment, (i) acquiring a fuel sample can furthercomprise determining the presence of the compound characterized byFormula I in the fuel sample.

In an embodiment, the analytical technique can evaluate fueladulteration by determining the amount of the compound characterized byFormula I in the marked fuel mixture, e.g., the amount of the compoundcharacterized by Formula I in the marked fuel composition, the amount ofthe compound characterized by Formula I in the fuel sample, etc.

In an embodiment, if the amount of the compound characterized by FormulaI in the fuel sample matches the control data (e.g., target markerconcentration) of the marked fuel composition, the fuel can be deemed tobe unadulterated fuel.

In an embodiment, if the amount of the compound characterized by FormulaI in the fuel sample does not match the control data (e.g., targetmarker concentration) of the marked fuel composition, the fuel can bedeemed to be adulterated fuel.

In an embodiment, if a compound characterized by Formula I is detectedin an unmarked fuel, the fuel can be deemed to be adulterated fuel.

In an embodiment, if a compound characterized by Formula I is detectedin a fuel marked with a marker other than the compound characterized byFormula I, the resulting fuel can be deemed to be adulterated fuel.

In an embodiment, a method of determining adulteration of a fuel cancomprise (i) acquiring a fuel sample; (ii) subjecting the fuel sample toGC-MS to yield GC-MS data; and (iii) comparing the GC-MS data of thefuel sample with the GC-MS data of the marked fuel composition (e.g.,control data of the marked fuel composition). In such an embodiment, themethod can further comprise determining an amount of the compoundcharacterized by Formula I present in the marked fuel composition and/orthe fuel sample based on the GC-MS data.

GC-MS enables both qualitative and quantitative analysis of mixtures ofcompounds. Generally, GC-MS is a combination of two techniques into asingle method of analysis for mixtures of compounds (e.g., marked fuelcomposition, marked fuel mixture, fuel sample, etc.). Gas chromatography(GC) is a very prevalent technique for the separation of complexmixtures such as petroleum products because of its high separation powerand low limits of detection when paired with a suitable detector like amass spectrometer. GC separates components of a mixture based ondifferences in the chemical properties between different mixturecomponents and based on their relative affinities for a stationary phaseof a GC column. As a sample (e.g., fuel sample) travels along the GCcolumn, the mixture components separate (e.g., some components willtravel faster than others). The mixture components will ideally exit theGC individually, and would enter the mass spectrometer (MS) for furthercharacterization. As will be appreciated by one of skill in the art, andwith the help of this disclosure, sometimes certain mixture componentswill travel together along the GC column, and will enter the MStogether; however, MS has the ability to discriminate between certainmixture components that elute (come off) together from the GC column.The different compounds can be retained by the GC column and then elutefrom the GC column at different times (e.g., retention times), and thiscan allow the MS downstream to analyze (e.g., capture, ionize,accelerate, deflect, detect, etc.) individually the eluted components.MS characterizes each component entering from the GC individually byionizing molecules (e.g., breaking each molecule into ionized fragments)and detecting these fragments using their mass-to-charge ratio.Nonlimiting examples of ionization methods suitable for use in MSinclude electron ionization (also known as electron impact), chemicalionization, electrospray ionization, matrix-assisted laserdesorption/ionization, inductively coupled plasma, photoionization, glowdischarge, field desorption, fast atom bombardment, thermospray, sparkionization, thermal ionization, and the like, or combinations thereof.

In an embodiment, the fuel sample and/or the marked fuel mixture can besubjected to GC-MS, wherein the ionization method of the MS compriseselectron ionization.

Generally, MS allows identification of amount and type of compounds(e.g., molecules) present in a sample by measuring the mass-to-chargeratio and abundance of gas-phase ions. MS ionizes chemical compounds togenerate charged molecules or molecule fragments and measures theirmass-to-charge ratios. The molecule fragments are actually charged ionswith a certain mass. The mass of the fragment divided by the charge iscalled the “mass-to-charge ratio” (m/z). Since most fragments have acharge of +1, the mass-to-charge ratio usually represents the molecularweight of the fragment. MS produces a mass spectrum for each analyzedcompound, wherein the x-axis represents the mass-to-charge ratio andwherein the y-axis represents the signal intensity (abundance) for eachof the fragments detected. As will be appreciated by one of skill in theart, and with the help of this disclosure, the mass spectrum produced bya given compound is essentially the same every time, and can be regardedas a “fingerprint” for the compound. This fingerprint can be used toidentify the compound.

The y-axis in the mass spectrum can be a relative abundance axis. Thepeak with the greatest abundance is usually referred to as a “basepeak,” and for the purpose of making a relative abundance axis the basepeak intensity is set to 100%, such that the entire mass spectrum isnormalized to the base peak. In some embodiments, the molecular ion peakcan be the base peak. In such embodiments, the entire mass spectrum canbe normalized to the molecular ion peak, wherein the molecular ion peakhas 100% relative abundance.

In other embodiments, a peak other than the molecular ion peak can bethe base peak. In such embodiments, all other fragment peaks and/ormolecular ion peak can be normalized with respect to the base peak,wherein the base peak has 100% relative abundance, to produce normalizedfragment peaks and/or a normalized molecular ion peak.

If a sample forms a molecular ion, it is likely to be the heaviest ion(e.g., ion with the greatest mass-to-charge ratio value) in the massspectrum, and as such allows the identification of the compound by itsmolecular weight. The molecular ion is generally an ion formed by theremoval from (positive ions) or addition to (negative ions) a moleculeof one electron without fragmentation of the molecular structure. Themass of the molecular ion corresponds to the sum of the masses of themost abundant naturally occurring isotopes of the various atoms thatmake up the molecule (with a correction for the masses of theelectron(s) lost or gained). As will be appreciated by one of skill inthe art, and with the help of this disclosure, some compounds do nothave a molecular ion present on the mass spectrum, because all of themolecular ions break into fragments.

As will be appreciated by one of skill in the art, and with the help ofthis disclosure, the way a compound (e.g., a molecule) fragments dependsupon the type of ionization used to ionize the compound. Further, aswill be appreciated by one of skill in the art, and with the help ofthis disclosure, the fragmentation pattern formed by an analyte willdepend on the ionization conditions and therefore is a controllableparameter within the analysis.

In an embodiment, a fuel sample and/or a marked fuel mixture can besubjected to GC-MS, wherein the MS ionization method comprises electronionization (EI), and wherein the ionization energy of the MS can beequal to or greater than about 70 eV, which effectively ionizes mostorganic compounds. In an embodiment, the extent of ionization iscontrolled to preferentially afford ionization of the analyte and heavymarker. This can be achieved by a variety of methods, including varyingthe EI voltage, use of chemical ionization with different chemicalpotentials, and photoionization with different strengths and wavelengthsof light as non-limiting examples.

In an embodiment, the compound characterized by Formula I when subjectedto GC-MS using electron ionization can produce at least one ion having amass-to-charge ratio of equal to or greater than about 300,alternatively from about 300 to about 600, alternatively from about 400to about 600, or alternatively from about 500 to about 600, at anionization energy of equal to or greater than about 70 eV.

In an embodiment, the compound characterized by Formula I when subjectedto GC-MS using electron ionization can produce at least one molecularion having a mass-to-charge ratio of equal to or greater than about 300,alternatively from about 300 to about 600, alternatively from about 400to about 600, or alternatively from about 500 to about 600, at anionization energy of equal to or greater than about 70 eV.

In an embodiment, the marked fuel composition can comprise at least twocompounds characterized by Formula I, wherein the marked fuelcomposition can be subjected to GC-MS. Each of the fuel markers of themarked fuel composition can display a unique mass spectrum profile, andcan provide for authenticating a fuel sample. GC-MS can yield a massspectrum displaying simultaneously information about more than one fuelmarker, provided that the fuel markers have a different molecularweight, e.g., their molecular ions have different mass-to-charge ratios.

In an embodiment, a method of determining adulteration of a fuel cancomprise subjecting to GC-MS a marked fuel mixture comprising (a) fuel;(b) a compound characterized by Formula I; and (c) a heavy compound,wherein the heavy compound comprises a compound of Formula I having atleast one atom replaced with an isotope tag. As will be appreciated byone of skill in the art, and with the help of this disclosure, MS caneasily distinguish between different isotopes of a given element, sinceMS separates and detects ions of slightly different masses, such as forexample isotopes having a mass-to-charge ratio differing by ±1 or more.

Generally, differences in mass among isotopes of an element are verysmall, and the less abundant isotopes of an element are typically veryrare. As such, if an isotope tag as disclosed herein is present in acompound, the signal of the isotope tag will be greater than the naturalabundance of such isotope, making it possible to identify the heavycompound comprising the isotope tag. As will be appreciated by one ofskill in the art, and with the help of this disclosure, the compoundcharacterized by Formula I, and the heavy compound, wherein the heavycompound comprises a compound of Formula I having at least one atomreplaced with an isotope tag, elute simultaneously or nearlysimultaneously in the GC, and are analyzed simultaneously or nearlysimultaneously on MS.

In an embodiment, the compound characterized by Formula I and the heavycompound comprising a compound of Formula I having at least one atomreplaced with an isotope tag can each display MS peaks that aredifferent (e.g., distinct, dissimilar, etc.) from each other, therebyenabling simultaneous detection of both the compound characterized byFormula I and the heavy compound.

Further, as will be appreciated by one of skill in the art, and with thehelp of this disclosure, the abundance of each peak corresponds to theamount of the compound that gave rise to that particular peak.

In an embodiment, the base peak of a heavy compound characterized byFormula I can comprise at least one isotope tag. In some embodiments,the base peak of a heavy compound characterized by Formula I cancomprise all isotope tags of the heavy compound characterized by FormulaI. In an embodiment, the molecular ion peak of a heavy compoundcharacterized by Formula I can comprise at least one isotope tag. Insome embodiments, the molecular ion peak of a heavy compoundcharacterized by Formula I can comprise all isotope tags of the heavycompound characterized by Formula I.

In an embodiment, a method of determining adulteration of a fuel cancomprise (i) acquiring a fuel sample; (ii) subjecting the fuel sample to¹³C NMR spectroscopy to yield ¹³C NMR data; and (iii) comparing the ¹³CNMR data of the fuel sample with the ¹³C NMR data of the marked fuelcomposition (e.g., control data of the marked fuel composition). In suchan embodiment, the method can further comprise determining an amount ofthe compound characterized by Formula I present in the composition andthe fuel sample based on the ¹³C NMR data. NMR spectroscopy is aresearch technique that exploits the magnetic properties of certainatomic nuclei, such as for example hydrogen (¹H NMR) or carbon (¹³CNMR). Generally, NMR spectroscopy relies on the phenomenon of nuclearmagnetic resonance and can provide detailed information about thestructure, dynamics, reaction state, and chemical environment ofmolecules. The intramolecular magnetic field around an atom in amolecule changes the resonance frequency, thus giving access to detailsof the electronic structure of a molecule.

In an embodiment, a method of determining adulteration of a fuel cancomprise subjecting to ¹³C NMR spectroscopy a marked fuel mixturecomprising (a) a fuel; (b) a compound characterized by Formula I; and(c) a heavy compound, wherein the heavy compound comprises a compound ofFormula I having at least one atom replaced with an isotope tag, whereinthe isotope tag comprises carbon-13 (¹³C).

In an embodiment, a method of determining adulteration of a fuel cancomprise (i) acquiring a fuel sample; (ii) subjecting the fuel sample tosurface enhanced Raman scattering spectroscopy (SERS) to yield SERSdata; and (iii) comparing the SERS data of the fuel sample with the SERSdata of the marked fuel composition (e.g., control data of the markedfuel composition). In such an embodiment, the fuel sample can further bea marked fuel mixture. Raman spectroscopy is a technique used to observevibrational, rotational, and other low-frequency modes in a molecule,which renders it sensitive to isotopic substitution, due tolow-frequency modes in a molecule being influenced by the weight of theindividual atoms in the bonds that lead to those modes. Generally, SERSis a surface-sensitive technique that enhances Raman scattering bymolecules adsorbed on rough metal surfaces or by nanostructures such asplasmonic-magnetic silica nanotubes. SERS can also be performed incolloidal solutions. SERS is an extremely sensitive analytical techniqueand it has the potential of detecting single molecules.

In an embodiment, a method of determining adulteration of a fuel cancomprise subjecting to SERS a marked fuel mixture comprising (a) a fuel;(b) a compound characterized by Formula I; and (c) a heavy compound,wherein the heavy compound comprises a compound of Formula I having atleast one atom replaced with an isotope tag.

In some embodiments, determining adulteration of a fuel can becomplicated by matrix effects. Generally, a “matrix” refers to anenvironment surrounding an analyte of interest (e.g., fuel marker), suchas for example fuel components, solvent, laundering agents, maskingagents, etc. In some cases, the matrix can influence the result ofdetecting a particular analyte, by interfering with the detection, ansuch interference can be referred for purposes of the disclosure hereinas “matrix effect(s).” In some cases, matrix components can enhancetransfer of analytes (e.g., fuel markers) through GC (matrix inducedresponse enhancement); in other cases, matrix components can decreaseanalyte responses (matrix induced diminishment). For purposes of thedisclosure herein, the term “matrix effects” encompasses the manydifferent root causes of error that can occur in GC-based or GC-MS-basedanalyses as a result of matrix related issues.

A conventional calibration process for a routine GC/MS analysis cangenerally involve creating a series of accurately prepared samples(“calibration standards”) containing known but varying concentrations ofan analyte of interest (e.g., fuel marker) in a suitable and readilyavailable solvent. The calibration standards can then be analyzed byGC-MS and a calibration curve can be generated by plotting an analyteresponse vs. a concentration of the analyte in the sample.Conventionally, the concentration of analyte in unknown samples can bedetermined by analyzing the unknown samples with the same methodology asthe calibration standards, followed by using the measured analyteresponse to mathematically derive the concentration of the analyte inthe unknown sample from the relationship described by the calibrationcurve. An increased accuracy of analyte detection (e.g., accurateanalyte quantitation) in GC-MS can be achieved when a solvent used tocreate the calibration standards is closely matched to the matrix of theunknown samples. For example, isolating an analyte from a matrix caninvolve a step of extracting the analyte from an aqueous solution intoan organic solvent, such as for example dichloromethane; it is likelythat the most accurate quantitation for the analyte could be achieved byusing a “matrix matched standard” method, wherein the calibrationstandards are prepared in the same organic solvent (e.g.,dichloromethane). However, in some instances, even matching the matrix(e.g., matching a predominant solvent environment around an analyte) canbe insufficient to achieve a desired level of analytical performance. Insuch instances, decreased analytical performance can manifest as matrixeffects (e.g., inaccurate quantitation, decreased method ruggedness, lowanalyte detectability, reporting of false positives or negative results,etc.).

In some embodiments, a method of determining adulteration of a fuel cancomprise subjecting a fuel sample to a method of separating at least aportion of the fuel marker from at least a portion of its fuel samplematrix by using any suitable methodology, such as for example solidphase extraction (SPE). Matrix effects can interfere in analysis ofGC-MS-based markers in fuels during fuel authentication, e.g., canprevent an accurate quantitation of fuel markers by GC-MS. For example,matrix effects can be problematic in fuel authentication analyses inareas or countries where fuel composition varies greatly as a result ofsuch areas or countries using more than one fuel stream source, whereinthe fuel specifications and/or compositions are different for at leasttwo of the fuel stream sources, due to such areas or countries onlyrefining a portion of their fuel used internally; such areas orcountries purchasing a portion of their fuel from outside suppliers;etc. Matrix effects can be greatly exacerbated by the fact that manyreal world samples (which can be of unknown pedigree) can be (and oftenare) adulterated with other substances (e.g., adulterants, launderingagents, etc.), such as other fuels types, industrial solvents, usedoils, and the like, or combinations thereof. Fuel adulteration isgenerally unknown prior to a fuel authentication analysis, and since theexistence of adulterants can be unknown, appropriate instrumentcalibration and generating a reliable calibration curve cannot be doneunder conventional methodologies.

In an embodiment, a method of determining adulteration of a fuel canfurther comprise subjecting a fuel sample (e.g., crude oil, asphaltmixes, diesel fuel, etc.) to SPE. Generally, SPE is a sample preparationtechnique that uses solid particles (e.g., chromatographic packingmaterial) usually contained in a cartridge type device (e.g., SPEcolumn), to chemically separate the different components of a sample,wherein samples are most often in a liquid state. The differentcomponents of a sample would generally elute in different fractions offthe SPE column. SPE is commonly used for removal of interferences fromsamples to facilitate subsequent analysis of such samples.

In some embodiments, a fuel (e.g., fuel sample, marked fuel mixture,etc.) can comprise a matrix, wherein the matrix can comprise anon-interfering portion of the matrix (e.g., non-interfering componentsof the matrix) and an interfering portion of the matrix (e.g.,interfering components of the matrix). The matrix generally refers to anenvironment surrounding the fuel marker and/or the heavy compound, aspreviously disclosed herein. In some embodiments, the interferingportion of the matrix can comprise masking agents. Generally, a maskingagent refers to any agent (e.g., compound, substance, etc.)intentionally added to a fuel with the purpose of interfering withauthenticating the fuel, e.g., with the purpose of interfering withaccurately detecting the presence and amount (e.g., concentration) ofmarkers (e.g., fuel markers) in the fuel. Nonlimiting examples ofmasking agents include any substance not native to the fuel, such ascrude oil, used oil, solvents, other chemicals, and the like, orcombinations thereof.

In an embodiment, a method of determining adulteration of a fuel cancomprise (i) contacting a fuel sample with a heavy compound to form amarked fuel mixture, wherein the fuel sample comprises a fuel and acompound characterized by Formula I (e.g., fuel marker), and wherein theheavy compound comprises the compound of Formula I having at least oneatom replaced with an isotope tag; (ii) subjecting the marked fuelmixture to SPE to yield a marked fuel mixture fraction, wherein at leasta portion of the fuel marker and at least a portion of the heavycompound elute together in the marked fuel mixture fraction; and (iii)subjecting to an analytical technique the marked fuel mixture fractionto determine fuel adulteration. In such an embodiment, the marked fuelmixture can comprise a non-interfering portion of the matrix,interfering components of the matrix, the compound characterized byFormula I, and the heavy compound. SPE can separate at least a portionof interfering components of the matrix from the compound characterizedby Formula I and the heavy compound, to yield a marked fuel mixturefraction comprising the compound characterized by Formula I and theheavy compound, wherein a concentration of the interfering components ofthe matrix in the marked fuel mixture fraction can be reduced by equalto or greater than about 75%, alternatively greater than about 80%,alternatively greater than about 85%, alternatively greater than about90%, or alternatively greater than about 95%, when compared to aconcentration of the interfering components of the matrix in the markedfuel mixture. Interfering compounds that might be present in the markedfuel mixture (e.g., masking agents, laundering agents, etc.) can beremoved by SPE, and as such the fraction containing the fuel marker andthe heavy compound can be further analyzed by any suitable analyticaltechnique (e.g., GC-MS). Even if SPE removes some of the fuel marker andcorresponding heavy compound from the marked fuel mixture, the ratio offuel marker to heavy compound is expected to remain substantially thesame, as both the marker and the corresponding heavy compound would beremoved from the fuel sample to the same extent due to having the samechemical formula differing only by the isotope tag(s). Further, theratio of fuel marker to corresponding heavy compound is expected toremain substantially the same even if the dilution (e.g., concentration)of the marker and the corresponding heavy compound changes in the markedfuel mixture fraction as compared to the marked fuel mixture. In someembodiments, the matrix comprises masking agents (e.g., interferingcomponents of the matrix).

In an embodiment, a fuel can be dually marked (e.g., fuel sample can bemarked with two different markers, wherein each marker can becharacterized by Formula I). In such an embodiment, a dually marked fuelsample can be contacted with heavy compounds corresponding to the twodifferent markers that mark the fuel to form a dually marked fuelmixture. The dually marked fuel mixture can be further subjected to SPEto obtain marked fuel mixture fractions, wherein each set of marker andcorresponding heavy compound can elute in separate (e.g., different,distinct) fractions. Interfering compounds that might be present in thefuel sample (e.g., masking agents) can be removed by SPE, and as suchthe fractions containing each set of marker and corresponding heavycompound can be further analyzed by any suitable analytical technique(e.g., GC-MS). While the present disclosure discusses a method ofdetermining adulteration of a dually marked fuel, it should beunderstood that such method or any steps thereof can be applied in amethod of determining adulteration of a fuel marked with any suitablenumber of markers, such as for example three, four, five, six, seven,eight, nine, ten, or more markers.

In an embodiment, a method of determining adulteration of a fuel canfurther comprise contacting a fuel sample with a heavy compound to forma marked fuel mixture; subjecting the marked fuel mixture to SPE;recovering a marked fuel mixture fraction, wherein the fractioncomprises a fuel marker and corresponding heavy compound, and whereinthe fraction is substantially free of interfering compounds (e.g.,masking agents) that could have been present in the fuel sample; andsubjecting the marked fuel mixture fraction to GC-MS analysis aspreviously described herein.

In an embodiment, a method of determining adulteration of a fuel canfurther comprise contacting a dually marked fuel sample withcorresponding heavy compounds to form a dually marked fuel mixture;subjecting the dually marked fuel mixture to SPE; recovering marked fuelmixture fractions, wherein separate fractions comprise each set of fuelmarker and corresponding heavy compound, and wherein such fractions aresubstantially free of interfering compounds (e.g., masking agents) thatcould have been present in the fuel sample; and subjecting the markedfuel mixture fractions to GC-MS analysis as previously described herein.

In an embodiment, a fuel marker can comprise a compound characterized byFormula I:

wherein X can be carbon (C), oxygen (O), or sulfur (S); R¹ and R² caneach independently be hydrogen, a C₁ to C₇ alkyl group, or a phenylgroup; R³ and R^(3′) can each independently be hydrogen or a methylgroup; R⁴ and R^(4′) can each independently be hydrogen, a methyl group,a tert-butyl group, a cyclohexyl group, or a phenyl group; R⁵ and R^(5′)can each independently be a C₆ or a C₇ alkyl group; R⁶ and R^(6′) caneach independently be hydrogen or a C₁ to C₄ alkyl group; and R⁷ andR^(7′) can each independently be hydrogen or a methyl group; and whereinthe compound characterized by Formula I when subjected to GC-MS usingelectron ionization can produce at least one ion having a mass-to-chargeratio of greater than about 300 at an ionization energy of equal to orgreater than about 70 eV.

In an embodiment, a method of forming a marked fuel composition cancomprise contacting (a) a fuel and (b) at least one compoundcharacterized by Formula I:

wherein X can be carbon (C), oxygen (O), or sulfur (S); R¹ and R² caneach independently be hydrogen, a C₁ to C₇ alkyl group, or a phenylgroup; R³ and R^(3′) can each independently be hydrogen or a methylgroup; R⁴ and R^(4′) can each independently be hydrogen, a methyl group,a tert-butyl group, a cyclohexyl group, or a phenyl group; R⁵ and R^(5′)can each independently be a C₆ or a C₇ alkyl group; R⁶ and R^(6′) caneach independently be hydrogen or a C₁ to C₄ alkyl group; and R⁷ andR^(7′) can each independently be hydrogen or a methyl group; and whereinthe compound characterized by Formula I when subjected to GC-MS usingelectron ionization can produce at least one ion having a mass-to-chargeratio of greater than about 300 at an ionization energy of equal to orgreater than about 70 eV.

In an embodiment, a method of determining adulteration of a fuel cancomprise subjecting to GC-MS a marked fuel composition comprising (a) afuel and (b) at least one compound characterized by Formula I:

wherein X can be carbon (C), oxygen (O), or sulfur (S); R¹ and R² caneach independently be hydrogen, a C₁ to C₇ alkyl group, or a phenylgroup; R³ and R^(3′) can each independently be hydrogen or a methylgroup; R⁴ and R^(4′) can each independently be hydrogen, a methyl group,a tert-butyl group, a cyclohexyl group, or a phenyl group; R⁵ and R^(5′)can each independently be a C₆ or a C₇ alkyl group; R⁶ and R^(6′) caneach independently be hydrogen or a C₁ to C₄ alkyl group; and R⁷ andR^(7′) can each independently be hydrogen or a methyl group; and whereinthe compound characterized by Formula I when subjected to GC-MS usingelectron ionization can produce at least one ion having a mass-to-chargeratio of greater than about 300 at an ionization energy of equal to orgreater than about 70 eV.

In an embodiment, a method of determining adulteration of a fuel cancomprise subjecting to GC-MS a marked fuel mixture comprising (a) afuel; (b) a compound characterized by Formula I:

wherein X can be carbon (C), oxygen (O), or sulfur (S); R¹ and R² caneach independently be hydrogen, a C₁ to C₇ alkyl group, or a phenylgroup; R³ and R^(3′) can each independently be hydrogen or a methylgroup; R⁴ and R^(4′) can each independently be hydrogen, a methyl group,a tert-butyl group, a cyclohexyl group, or a phenyl group; R⁵ and R^(5′)can each independently be a C₆ or a C₇ alkyl group; R⁶ and R^(6′) caneach independently be hydrogen or a C₁ to C₄ alkyl group; and R⁷ andR^(7′) can each independently be hydrogen or a methyl group; and (c) anda heavy compound, wherein the heavy compound comprises a compound ofFormula I having at least one atom replaced with an isotope tag,alternatively a plurality of the atoms are isotopically substituted. Insuch an embodiment, the isotope tag comprises deuterium (²H).

In an embodiment, a method of determining adulteration of a fuel cancomprise (i) contacting a fuel sample with a heavy compound to form amarked fuel mixture, wherein the fuel sample comprises a fuel and acompound characterized by Formula I:

wherein X can be carbon (C), oxygen (O), or sulfur (S); R¹ and R² caneach independently be hydrogen, a C₁ to C₂₀ alkyl group, or a C₆ to C₁₀aryl group; R³ and R^(3′) can each independently be hydrogen or a C₁ toC₄ alkyl group; R⁴ and R^(4′) can each independently be hydrogen, a C₁to C₄ alkyl group, a C₄ to C₁₀ cycloalkyl group, or a C₆ to C₁₀ arylgroup; R⁵ and R^(5′) can each independently be a C₄ to C₁₀ alkyl group;R⁶ and R^(6′) can each independently be hydrogen or a C₁ to C₆ alkylgroup; and R⁷ and R^(7′) can each independently be hydrogen or a C₁ toC₄ alkyl group; and wherein the heavy compound comprises the compound ofFormula I having at least one atom replaced with deuterium; (ii)subjecting the marked fuel mixture to solid phase extraction (SPE) toyield a marked fuel mixture fraction, wherein at least a portion of thecompound characterized by Formula I and at least a portion of the heavycompound elute together in the marked fuel mixture fraction; and (iii)subjecting to gas chromatography-mass spectrometry (GC-MS) the markedfuel mixture fraction to determine fuel adulteration, wherein each ofthe compound characterized by Formula I and the heavy compound whensubjected to GC-MS using electron ionization produces at least one ionhaving a mass-to-charge ratio of from about 300 to about 600 at anionization energy of equal to or greater than about 70 eV. In such anembodiment, the compound characterized by Formula I can have StructureF:

and the heavy compound can have d-Structure F:

In an embodiment, the marked fuel compositions as disclosed hereinadvantageously display improvements in one or more characteristics, whencompared to similar compositions lacking a fuel marker as disclosedherein. For example, the marked fuel compositions can advantageouslydisplay enhanced detectability, e.g., a lower amount of fuel marker canbe used to mark fuel compositions and enable determining the fueladulteration.

In an embodiment, the fuel markers as disclosed herein cannot beextracted (e.g., removed, taken out, etc.) from a marked fuelcomposition by conventional means. For example, the fuel marker cannotbe substantially differentially adsorbed from a marked fuel compositionusing conventional inexpensive adsorbents; cannot be removed byextraction with acids, bases, or immiscible solvents; cannot be easilyoxidized, reduced or reacted with common reagents to effectively removethe fuel marker; and the like. Further, it should be difficult (e.g.,not practical, not feasible financially) to disguise the presence of thefuel marker by masking the marker via reactions with masking agents.

In an embodiment, the fuel markers as disclosed herein should not alter(e.g., modify, change, interfere with, etc.) the properties of the fuel.In an embodiment, the fuel markers as disclosed herein can beadvantageously stable under conditions (e.g., environmental conditions)that the fuel can be subjected to.

In an embodiment, the fuel markers as disclosed herein canadvantageously display an adequate solubility in solvents for markerdelivery. For example, the fuel markers can be characterized by asolubility in solvents of equal to or greater than about 50%,alternatively from about 50% to about 20%, or alternatively from about20% to about 5% at 25° C.

In an embodiment, the fuel markers as disclosed herein canadvantageously allow qualitative and/or quantitative authentication offuels, such as for example by GC-MS analysis. In an embodiment, the fuelmarkers as disclosed herein can advantageously allow for the use ofsmall amounts (e.g., from about 1 ppb to about 50 ppm, based on thetotal weight of the marked fuel composition) of fuel markers as comparedto other conventional markers.

In an embodiment, the fuel markers as disclosed herein can allow forusing and detecting more than one marker simultaneously, such as forexample by GC-MS. In such an embodiment, authentication of a fuel can beaccomplished by comparing more than one variable, e.g., bysimultaneously detecting the presence and/or concentration of more thanone fuel marker by GC-MS, for example.

In an embodiment, fuel markers and methods of using same as disclosedherein can advantageously mitigate matrix effects. Conventionalanalytical methods (e.g., matrix matched standard-based calibrationswith bracketing standards) for analyzing fuel markers cannot accuratelyquantify markers in refined petroleum products (e.g., fuels). In anembodiment, a method of using the fuel markers to determine fueladulteration as disclosed herein can advantageously display improveddetection accuracy, without adding substantial sample preparation steps(which can be both costly and time consuming), when compared toconventional detection methods. Additional advantages of the marked fuelcompositions and methods of producing and using same as disclosed hereincan be apparent to one of skill in the art viewing this disclosure.

EXAMPLES

The subject matter having been generally described, the followingexamples are given as particular embodiments of the disclosure and todemonstrate the practice and advantages thereof. It is understood thatthe examples are given by way of illustration and are not intended tolimit the specification of the claims to follow in any manner.

Example 1

The compound characterized by Structure F (i.e.,bis(5-(tert-butyl)-2-methyl-4-(pentyloxy)phenyl)sulfane) was synthesizedby reaction of 4,4′-thiobis(2-(tert-butyl)-5-methylphenol)(4,4′-thiobis(6-tert-butyl-m-cresol)) with 1-bromopentane, according tothe following reaction scheme:

4,4′-thiobis(2-(tert-butyl)-5-methylphenol)(4,4′-thiobis(6-tert-butyl-m-cresol)) (1 equivalent (eq), 10 g, 27.89mmol), potassium carbonate (2.5 eq, 9.6363 g, 69.725 mmol, 138.205g/mol), and 1-bromopentane (2.1 eq, 8.8463 g, 7.3 mL, 58.569 mmol,151.04 g/mol, d=1.218 g/mL) were dissolved in N,N-dimethylformamide(DMF, 90 mL) at 90° C. The reaction was stirred until complete asdetermined by thin layer chromatography (TLC). The reaction was pouredinto water and extracted with ethyl acetate. The aqueous layer wasdiscarded and the ethyl acetate was back-extracted three times withbrine to remove residual DMF. The resulting organic solution was driedwith magnesium sulfate, filtered, and concentrated on a rotaryevaporator. The crude product was recrystallized from methanol,filtered, and then washed with cold methanol. The product was dried at50° C. under high vacuum for 12 hours to yield a fine white powder(compound characterized by Structure F:bis(5-(tert-butyl)-2-methyl-4-(pentyloxy)phenyl)sulfane). The yield was8.4211 g (60.5%).

Example 2

The compound characterized by Structure B (i.e.,bis(4-(heptyloxy)phenyl)sulfane) was synthesized by reaction of4,4′-thiodiphenol (bis(4-hydroxyphenyl)sulfide) with 1-bromoheptane,according to the following reaction scheme:

4,4′-thiodiphenol (bis(4-hydroxyphenyl) sulfide) (1 eq, 10 g, 45.8mmol), potassium carbonate (2.5 eq, 15.8245 g, 114.5 mmol, 138.205g/mol), and 1-bromoheptane (2.5 eq, 20.5070 g, 18 mL, 114.5 mmol, 179.10g/mol, d=1.14 g/mL) were dissolved in DMF (100 mL) at 80° C. Thereaction was stirred until complete as determined by TLC. The reactionwas poured into water and extracted with dichloromethane (DCM). Theaqueous layer was discarded and the DCM was back-extracted three timesto remove residual DMF. The resulting organic solution was dried withsodium sulfate, filtered, and concentrated on a rotary evaporator. Theproduct was recrystallized from ethanol, filtered, and then washed withcold ethanol. The product was subsequently put through a silica plugwith 50-50 hexanes-DCM and concentrated on a rotary evaporator to yielda white powder (compound characterized by Structure B:bis(4-(heptyloxy)phenyl)sulfane). The product was dried under highvacuum for 24 hours at 50° C. to remove residual solvents and1-bromoheptane. The yield was 5 g (26.3%)

Example 3

The compound characterized by Structure C (i.e.,bis(4-(heptyloxy)-3-methylphenyl)sulfane) was synthesized by reaction of4,4′-thiobis(2-methylphenol) (bis(4-hydroxy-3-methylphenyl) sulfide)with 1-bromoheptane, according to the following reaction scheme:

4,4′-thiobis(2-methylphenol) (bis(4-hydroxy-3-methylphenyl) sulfide) (1eq, 10 g, 40.6 mmol), potassium carbonate (3.0 eq, 16.8334 g, 121.8mmol, 138.205 g/mol), and 1-bromoheptane (3 eq, g, 21.8144 g, 19.2 mL,121.8 mmol, 179.10 g/mol, d=1.14 g/mL) were dissolved in DMF (150 mL) at80° C. The reaction was stirred until complete as determined by TLC. Thereaction was poured into water and extracted with ethyl acetate. Theaqueous layer was discarded and the ethyl acetate was back-extractedthree times to remove residual DMF. The resulting organic solution wasdried with sodium sulfate, filtered, and concentrated on a rotaryevaporator. The product was recrystallized from ethanol, filtered, andthen washed with cold ethanol. The product (compound characterized byStructure C: bis(4-(heptyloxy)-3-methylphenyl)sulfane) was dried at 50°C. under high vacuum for 24 hours to remove residual 1-bromoheptane. Theyield was 9.9320 g (55.3%).

Example 4

The compound characterized by Structure A (i.e.,4,4′-oxybis((heptyloxy)benzene)) was synthesized by reaction of4,4′-oxydiphenol (4,4′-dihydroxydiphenyl ether) with 1-bromopentane,according to the following reaction scheme:

4,4′-oxydiphenol (4,4′-dihydroxydiphenyl ether) (1 eq, 10 g, 49.5 mmol),potassium carbonate (2.5 eq, 17.1029 g, 123.75 mmol, 138.205 g/mol), and1-bromoheptane (2.5 eq, 22.1636 g, 19.5 mL, 123.75 mmol, 179.10 g/mol,d=1.14 g/mL) were dissolved in DMF (100 mL) at 80° C. The reaction wasstirred until complete as determined by TLC. The reaction was pouredinto water and filtered. The crude product was taken up in methanol andheated while stirring, followed by sonication. The suspension was thenfiltered warm and the product washed with room temperature methanol toyield a white powder (compound characterized by Structure A:4,4′-oxybis((heptyloxy)benzene)). The yield was 16.3 g (83.6%).

Example 5

A deuterated compound characterized by Structure F, d-Structure F (i.e.,bis(5-(tert-butyl)-2-methyl-4-(pentyl-d₂₂-oxy)phenyl)sulfane) wassynthesized by reaction of 4,4′-thiobis(2-(tert-butyl)-5-methylphenol)(4,4′-thiobis(6-tert-butyl-m-cresol)) with deuterated 1-bromopentane(1-bromopentane-d₁₁), according to the following reaction scheme:

4,4′-thiobis(2-(tert-butyl)-5-methylphenol)(4,4′-thiobis(6-tert-butyl-m-cresol)) (1 eq, 1.1641 g, 3.2467 mmol),potassium carbonate (2.1 eq, 0.9423 g, 6.8181 mmol, 138.205 g/mol), and1-bromopentane-d₁₁ (1.9 eq, 1 g, 6.1687 mmol, 162.11 g/mol) weredissolved in 10 mL DMF at 85° C. The reaction was stirred until completeas determined by TLC. The reaction was poured into water and extractedwith DCM. The aqueous layer was discarded and the DCM was back-extractedthree times to remove residual DMF. The resulting organic solution wasdried with sodium sulfate, filtered, and concentrated on a rotaryevaporator. The product was subsequently put through a silica plug with50-50 hexanes-DCM and concentrated on a rotary evaporator. The product(deuterated compound characterized by Structure F, d-Structure F:bis(5-(tert-butyl)-2-methyl-4-(pentyl-d₂₂-oxy)phenyl)sulfane) was driedunder high vacuum for 24 hours at 50° C. to remove residual1-bromopentane. The yield was 1 g (59.1%).

Example 6

A deuterated compound characterized by Structure B, d-Structure B (i.e.,bis(4-(heptyl-d₃₀-oxy)phenyl)sulfane) was synthesized by reaction of4,4′-thiodiphenol (bis(4-hydroxyphenyl) sulfide) with deuterated1-bromoheptane (1-bromoheptane-d₅), according to the following reactionscheme:

4,4′-thiodiphenol (bis(4-hydroxyphenyl) sulfide) (1 eq, 1.1832 g, 5.4mmol), potassium carbonate (2.1 eq, 1.57 g, 11.4 mmol, 138.205 g/mol),and 1-bromoheptane-d₅ (1.9 eq, 2 g, 10.3 mmol, 194.19 g/mol) weredissolved in DMF (50 mL) at 85° C. The reaction was stirred untilcomplete as determined by TLC. The reaction was poured into water andextracted with DCM. The aqueous layer was discarded and the DCM wasback-extracted three times to remove residual DMF. The resulting organicsolution was dried with sodium sulfate, filtered, and concentrated on arotary evaporator. The product was recrystallized from ethanol,filtered, and then washed with cold ethanol. The product wassubsequently put through a silica plug with 50-50 hexanes-DCM andconcentrated on a rotary evaporator to yield a white powder (deuteratedcompound characterized by Structure B, d-Structure B:bis(4-(heptyl-d₃₀-oxy)phenyl)sulfane). The product was dried under highvacuum for 24 hours at 50° C. to remove residual solvents and1-bromoheptane. The yield was 1.2 g (50%).

Example 7

The identity of fuel samples was investigated. More specifically, theconcentration of fuel markers in various fuel samples was investigated.

Sample and Standard Preparation.

Internal standard solutions were prepared by accurately diluting thefuel sample and adding a heavy fuel marker as internal standard to eachdiluted sample. For fuel marking, a concentrate of fuel marker intoluene was prepared to a concentration of 50 ppm (m/v) and added to thediesel fuel to yield a final concentration of marker in diesel of 100ppb (m/v).

Instrumentation.

GC-MS analyses were conducted on an Agilent 7890B Gas Chromatographequipped with an Agilent 5977A Mass Selective Detector and an Agilent7650 Automatic Liquid Sampler. A DB-35 ms Ultra Inert column (15 m×0.250mm×0.25 μm) was connected directly to a split/splitless inlet and to themass spectrometer, and a helium carrier was utilized. The methodconditions for all analyses were as follows: constant flow of 1.5mL/min, inlet temperature of 340° C., pulsed splitless injection at 40psi for 0.5 min, temperature program at 150° C. for 0.5 min, then a 30°C./min ramp to 300° C. followed by a 20° C./min ramp to 340° C. (4 minhold), and a MS transfer line temperature of 340° C. MS quadrupole wasoperated in selected ion monitoring (SIM) mode with two ions beingmonitored for each analyte, and automated tuning was performed using theETUNE parameter set.

For analysis, internal standard and sample were co-injected into theinlet via a 5 μL syringe as a sandwich injection where 1 μL of samplewas co-injected with 0.5 μL of the internal standard solution. Forsamples in which the injection of no internal standard was desired, asandwich injection was still performed so as to maintain the sameanalytical methodology for comparison purposes, only the internalstandard solution was replaced by a sample of toluene.

GC-MS Analysis.

All samples were analyzed in triplicate and the three results averagedfor reporting purposes. A bracketing standard of the marker in locallyobtained diesel fuel was injected every fifth injection and used tocalculate the concentrations of the 5 diesel fuel samples in the study.

Samples of diesel fuels (sample #1, sample #2, sample #3, sample #4, andsample #5) from various fuel stations across the globe were accuratelymarked with a compound characterized by Structure F at a concentrationof 100 ppb (m/v). These samples were analyzed in triplicate and theresulting data are displayed in Table 1 (ISTD=internal standardcharacterized by d-Structure F) and FIG. 1.

TABLE 1 Calculated Fuel Marker Fuel Marker Sample ID ISTD ResponseResponse Concentration (ppb) Samples with ISTD Diesel Standard 182,69730,318 — Sample #5 143,764 25,061 105.8 Sample #2 29,046 5,046 105.5Sample #1 69,070 13,265 116.6 Sample #3 192,864 30,577 96.2 Sample #4175,005 29,966 103.9 Diesel Standard 180,052 29,843 — Sample #5 138,81724,761 108.3 Sample #2 28,689 4,818 101.9 Sample #1 70,016 12,845 111.4Sample #3 190,001 30,702 98.1 Sample #4 179,007 29,391 99.7 DieselStandard 179,656 29,852 — Sample #5 142,773 24,382 103.7 Sample #228,408 5,029 107.5 Sample #1 69,699 13,002 113.2 Sample #3 191,56430,497 96.6 Sample #4 179,568 29,387 99.3 Diesel Standard 178,788 29,810— Samples without ISTD Diesel Standard — 30,663 — Sample #5 — 25,70983.4 Sample #2 — 5,115 16.6 Sample #1 — 13,292 43.1 Sample #3 — 31,964103.7 Sample #4 — 29,987 97.3 Diesel Standard — 30,994 — Sample #5 —25,500 82.7 Sample #2 — 5,090 16.5 Sample #1 — 13,353 43.3 Sample #3 —31,966 103.6 Sample #4 — 30,169 97.8 Diesel Standard — 30,711 — Sample#5 — 25,389 82.3 Sample #2 — 5,109 16.6 Sample #1 — 13,272 43.0 Sample#3 — 31,470 102.0 Sample #4 — 30,442 98.6 Diesel Standard — 31,015 —

For the standard analysis, a standard sample of diesel fuel obtainedlocally (diesel standard) was marked with the compound characterized byStructure F at a concentration of 100 ppb (m/v) and run every fifthinjection to serve as a bracketing standard. The average response fromthe bracketing standards were determined and used to calculate theconcentration of marker in the different fuel samples. FIG. 2 displaysextracted ion chromatograms (498.3 m/z) for sample #1 and sample #3. Insample #3, the suppression of the fuel marker is clearly evident ascompared to sample #1, as area counts for the marker around 6.7 minutesare very different for the sample concentration of marker in bothsamples.

When the same samples were analyzed and a deuterated internal standardwas added (via co-injection for this example), the calculatedconcentrations were far more accurate, as seen in Table 1 and FIG. 1.The average predicted value using conventional bracketing standardmethodology was 69 ppb for the five diesel samples (sample #1, sample#2, sample #3, sample #4, and sample #5), whereas while using theinternal standard methodology as described here, the averageconcentration for the five diesel samples was 104 ppb. The internalstandard deuterated compound and the fuel marker being suppressed by thematrix to the same extent resulted in a dramatic improvement inaccuracy. Therefore, by taking a ratio of responses of the fuel markerto internal standard (i.e., fuel marker response/internal standardresponse), instead of just the fuel marker response, the signalsuppression can be mitigated and a much more accurate result can bedetermined.

Data Analysis.

The data was analyzed by using a conventional bracketing standardapproach, wherein a standard sample (labeled herein “Diesel Standard”)was a sample of diesel to which 100 ppb of marker (characterized byStructure F) has been added. During the analytical sequence, the “DieselStandard” was injected prior to (e.g., preceding) and following (e.g.,succeeding) the samples of unknown marker concentration. Generally, if alarge number of samples of unknown marker concentration have to beanalyzed, then a standard sample can be injected every 5-10 injectionsof samples of unknown marker concentration. In all cases, the standardsample was the same. In calculating the marker concentration of thesamples (#1, #2, #3, #4, #5, etc.), the response of the marker in thestandard injections surrounding (or bracketing: preceding, succeeding,etc.) the samples was averaged and the response of each sample wasdivided by the average response of the standard sample (e.g., thebracketing standard) and multiplied by the concentration of the markerin the standard sample according to equation (1):

$\begin{matrix}{C_{x} = {2 \times \frac{R_{x}}{\left( {R_{{Std}\mspace{14mu} 1} + R_{{Std}\mspace{14mu} 2}} \right)} \times C_{Std}}} & (1)\end{matrix}$wherein C_(x)=concentration of the marker in sample X of unknown markerconcentration; wherein R_(x)=marker response in the sample X of unknownmarker concentration; wherein R_(Std 1)=marker response of the standardsample preceding the sample X of unknown marker concentration; whereinR_(Std 2)=marker response of the standard sample succeeding the sample Xof unknown marker concentration; wherein C_(Std)=concentration of themarker in the standard sample; and wherein R_(Std 1) and R_(Std 2) aredifferent injections of the same standard sample having a markerconcentration of C_(Std). For purposes of the disclosure herein,“response” refers to the magnitude of the analytical signal or response.Similarly, the concentration of the marker in fuel samples can becalculated by utilizing the ISTD as described herein, according toequation (2):

$\begin{matrix}{C_{x} = {2 \times \frac{{RR}_{X}}{\left( {{RR}_{{Std}\mspace{14mu} 1} + {RR}_{{Std}\mspace{14mu} 2}} \right)} \times C_{Std}}} & (2)\end{matrix}$wherein C_(x)=concentration of the marker in sample X of unknown markerconcentration; wherein RR_(X)=marker response ratio, or markerresponse/ISTD response for sample X of unknown marker concentration;wherein RR_(Std 1)=marker response ratio, or marker response/ISTDresponse of the standard sample preceding the sample X of unknown markerconcentration; wherein RR_(Std 2)=marker response ratio, or markerresponse/ISTD response of the standard sample succeeding the sample X ofunknown marker concentration; wherein C_(Std)=concentration of themarker in the standard sample; and wherein R_(Std 1) and R_(Std 2) aredifferent injections of the same standard sample having a markerconcentration of C_(Std). As will be appreciated by one of skill in theart, and with the help of this disclosure, while the concentrations werecalculated herein by using a single point calibration for simplicity,the principles of marker to internal standard response ratios can beapplied to any multipoint calibration curve or calibration process toenhance the accuracy of the calculated marker concentration.

It is noteworthy from the data collected (Table 1, FIGS. 1 and 2) thateven using a matrix matched standard gave very poor accuracy whenanalyzing diesel samples of different origin. These data speak to thefact that diesel fuel, and virtually all hydrocarbon-based fuels can behighly variable in nature. The source of the crude oil, refiningconditions, age, and environmental storage conditions all have adramatic impact on the chemical composition of the fuel. Further, thesedifferences can have a significant impact on the analysis of chemicalfuel markers added to fuels to aide in theiridentification/authentication.

Example 8

The identity of fuel samples was investigated. More specifically, theconcentration of fuel markers in various fuel samples was investigatedprior to and subsequent to solid phase extraction (SPE). Fuel samplesand analysis were prepared and conducted as described in Example 7.

Samples were acquired and marked with a compound characterized byStructure F as described in Example 7. Sample #1, sample #2, and sample#5 of Example 7 were analyzed prior to and subsequent to SPE. Upon SPE,the samples were labeled sample #1a, sample #2a, and sample #5a,respectively. For SPE analysis, a solution of ISTD (characterized byd-Structure F) in hexane (3 mL) (e.g., ISTD hexane solution) was addedto 0.225 mL of the fuel sample of unknown marker concentration to forman unknown sample in ISTD hexane solution, which was mixed to ensurecomplete dissolution. A 1 g silica gel SPE cartridge was conditionedwith 5 mL of hexane prior to the addition of 2 mL of the unknown samplein ISTD hexane solution. After the entire unknown sample in ISTD hexanesolution passed through the SPE column, the SPE column was rinsed with16 mL of hexane to remove interferences from the sample of unknownmarker concentration. The ISTD and marker were then eluted from the SPEcolumn with 2 mL of toluene into a vial which was then analyzed directlyvia GC-MS.

All samples were analyzed in triplicate and the resulting data aredisplayed in Table 2 (ISTD=internal standard characterized byd-Structure F).

TABLE 2 Calculated Fuel Marker Fuel Marker Sample ID ISTD ResponseResponse Concentration (ppb) Samples Post-SPE Cleanup Diesel Standard75,700 2,227 — Sample #5a 118,209 3841 96.5 Sample #2a 128,047 4491104.1  Sample #1a 130,170 4530 103.3  Diesel Standard 84,104 2,474 —Sample #5a 120,835 3,976 97.7 Sample #2a 129,746 4,606 105.4  Sample #1a128,500 4,506 104.1  Diesel Standard 88,641 2,667 — Sample #5a 134,8584,472 98.4 Sample #2a 128,014 4,522 104.9  Sample #1a 139,587 4,968105.6  Diesel Standard 92,185 2,795 — Samples Pre-SPE Cleanup DieselStandard — 30,663 — Sample #5 — 25,709 83.4 Sample #2 — 5,115 16.6Sample #1 — 13,292 43.1 Diesel Standard — 30,994 — Sample #5 — 25,50082.7 Sample #2 — 5,090 16.5 Sample #1 — 13,353 43.3 Diesel Standard —30,711 — Sample #5 — 25,389 82.3 Sample #2 — 5,109 16.6 Sample #1 —13,272 43.0 Diesel Standard — 31,015 —

FIG. 3A displays extracted ion chromatograms (498.4 m/z) for sample #1,sample #2 and sample #5, prior to SPE. FIG. 3B displays extracted ionchromatograms (498.4 m/z) for sample #1a, sample #2a and sample #5a,subsequent to SPE. As seen from FIG. 3B as compared to FIG. 3A, when theanalyzed samples were subjected to SPE, the calculated concentrationswere far more accurate. This dramatic increase in accuracy stems fromthe fact that the interferences present in the diesel samples, whichdramatically impact the accurate quantitation of the marker, are removedby the SPE process and hence the responses obtained from the analysisare more consistent across the fuel samples, similarly to the inclusionof the ISTD in the analysis, which provides additional enhanced accuracyto the analysis.

For the purpose of any U.S. national stage filing from this application,all publications and patents mentioned in this disclosure areincorporated herein by reference in their entireties, for the purpose ofdescribing and disclosing the constructs and methodologies described inthose publications, which might be used in connection with the methodsof this disclosure. Any publications and patents discussed herein areprovided solely for their disclosure prior to the filing date of thepresent application. Nothing herein is to be construed as an admissionthat the inventors are not entitled to antedate such disclosure byvirtue of prior invention.

In any application before the United States Patent and Trademark Office,the Abstract of this application is provided for the purpose ofsatisfying the requirements of 37 C.F.R. §1.72 and the purpose stated in37 C.F.R. §1.72(b) “to enable the United States Patent and TrademarkOffice and the public generally to determine quickly from a cursoryinspection the nature and gist of the technical disclosure.” Therefore,the Abstract of this application is not intended to be used to construethe scope of the claims or to limit the scope of the subject matter thatis disclosed herein. Moreover, any headings that can be employed hereinare also not intended to be used to construe the scope of the claims orto limit the scope of the subject matter that is disclosed herein. Anyuse of the past tense to describe an example otherwise indicated asconstructive or prophetic is not intended to reflect that theconstructive or prophetic example has actually been carried out.

The present disclosure is further illustrated by the following examples,which are not to be construed in any way as imposing limitations uponthe scope thereof. On the contrary, it is to be clearly understood thatresort can be had to various other aspects, embodiments, modifications,and equivalents thereof which, after reading the description herein, canbe suggest to one of ordinary skill in the art without departing fromthe spirit of the present invention or the scope of the appended claims.

ADDITIONAL DISCLOSURE

A first embodiment, which is a method of forming a compositioncomprising contacting (a) a fuel and (b) at least one compoundcharacterized by Formula I:

wherein X can be carbon (C), oxygen (O), or sulfur (S); R¹ and R² caneach independently be hydrogen, a C₁ to C₂₀ alkyl group, or a C₆ to C₁₀aryl group; R³ and R^(3′) can each independently be hydrogen or a C₁ toC₄ alkyl group; R⁴ and R^(4′) can each independently be hydrogen, a C₁to C₄ alkyl group, a C₄ to C₁₀ cycloalkyl group, or a C₆ to C₁₀ arylgroup; R⁵ and R^(5′) can each independently be a C₄ to C₁₀ alkyl group;R⁶ and R^(6′) can each independently be hydrogen or a C₁ to C₆ alkylgroup; and R⁷ and R^(7′) can each independently be hydrogen or a C₁ toC₄ alkyl group; and wherein the compound characterized by Formula I whensubjected to gas chromatography-mass spectrometry (GC-MS) using electronionization produces at least one ion having a mass-to-charge ratio offrom about 300 to about 600 at an ionization energy of equal to orgreater than about 70 eV.

A second embodiment, which is the method of the first embodiment,wherein X is O or S and R¹ and R² are lone non-bonding electron pairs.

A third embodiment, which is the method of any one of the first and thesecond embodiments, wherein X is O and wherein the compoundcharacterized by Formula I has Structure A:

A fourth embodiment, which is the method of any one of the first and thesecond embodiments, wherein X is S and wherein the compoundcharacterized by Formula I has any of Structures B-F:

A fifth embodiment, which is the method of the first embodiment, whereinX is C and R¹ and R² each independently are selected from the groupconsisting of a methyl group, an ethyl group, a n-propyl group, aniso-propyl group, a n-butyl group, an iso-butyl group, a sec-butylgroup, a tert-butyl group, a pentyl group, a n-pentyl group, aniso-pentyl group, a sec-pentyl group, a hexyl group, a heptyl group, anoctyl group, a nonyl group, a decyl group, a undecyl group, a dodecylgroup, a tridecyl group, a tetradecyl group, a pentadecyl group, ahexadecyl group, a heptadecyl group, an octadecyl group and a nonadecylgroup.

A sixth embodiment, which is the method of the first embodiment, whereinthe compound characterized by Formula I has any of Structures G-O:

A seventh embodiment, which is the method of the first embodiment,wherein X is C and R¹ and R² can each independently be hydrogen, a C₁ toC₁₀ alkyl group, or a C₆ to C₁₀ aryl group.

An eighth embodiment, which is the method of the seventh embodiment,wherein the C₆ to C₁₀ aryl group is phenyl, a substituted phenyl, tolyl,a substituted tolyl, xylyl or a substituted xylyl.

A ninth embodiment, which is the method of any one of the seventh andthe eighth embodiments, wherein the compound characterized by Formula Ihas Structure P:

A tenth embodiment, which is the method of the first embodiment, whereinX is C and R³ and R^(3′) can each independently be a methyl group orhydrogen.

An eleventh embodiment, which is the method of the first embodiment,wherein X is C and R⁴, R^(4′), R⁵, and R⁵ can each independently be a C₁to C₁₀ alkyl group, a C₄ to C₁₀ cycloalkyl group, or a C₆ to C₁₀ arylgroup.

A twelfth embodiment, which is the method of the eleventh embodiment,wherein R⁵ and R^(5′) are both a pentyl group or a heptyl group.

A thirteenth embodiment, which is the method of any one of the eleventhand the twelfth embodiments, wherein the C₄ to C₁₀ cycloalkyl group is acyclobutyl group, a substituted cyclobutyl group, a cyclopentyl group, asubstituted cyclopentyl group, a cyclohexyl group, a substitutedcyclohexyl group, a cycloheptyl group, a substituted cycloheptyl group,a cyclooctyl group, or a substituted cyclooctyl group.

A fourteenth embodiment, which is the method of the first embodiment,wherein X is C, R¹ and R² are a methyl group, and R⁵ and R^(5′) are botha C₄ to C₁₀ alkyl group.

A fifteenth embodiment, which is the method of any one of the firstthrough the fourteenth embodiments, wherein the fuel comprises gasoline,diesel, jet fuel, kerosene, non-petroleum derived fuels, alcohol fuels,ethanol, methanol, propanol, butanol, biodiesel, maritime fuels, orcombinations thereof.

A sixteenth embodiment, which is the method of any one of the firstthrough the fifteenth embodiments, wherein the compound characterized byFormula I is present in the composition in an amount of from about 1 ppbto about 50 ppm, based on the total weight of the composition.

A seventeenth embodiment, which is the method of any one of the firstthrough the sixteenth embodiments, wherein the composition comprises atleast 2 compounds characterized by Formula I.

An eighteenth embodiment, which is the method of the seventeenthembodiment further comprising (i) acquiring a fuel sample; (ii)subjecting the fuel sample to GC-MS to yield GC-MS data; and (iii)comparing the GC-MS data of the fuel sample with the GC-MS data of thecomposition.

A nineteenth embodiment, which is the method of the eighteenthembodiment further comprising determining an amount of the compoundcharacterized by Formula I present in the composition and the fuelsample based on the GC-MS data.

A twentieth embodiment, which is the method of any one of the firstthrough the nineteenth embodiments further comprising subjecting thecomposition to surface enhanced Raman scattering spectroscopy.

A twenty-first embodiment, which is the method of any one of the firstthrough the twentieth embodiments further comprising subjecting thecomposition to nuclear magnetic resonance spectroscopy.

While embodiments of the disclosure have been shown and described,modifications thereof can be made without departing from the spirit andteachings of the invention. The embodiments and examples describedherein are exemplary only, and are not intended to be limiting. Manyvariations and modifications of the invention disclosed herein arepossible and are within the scope of the invention.

Accordingly, the scope of protection is not limited by the descriptionset out above but is only limited by the claims which follow, that scopeincluding all equivalents of the subject matter of the claims. Each andevery claim is incorporated into the specification as an embodiment ofthe present invention. Thus, the claims are a further description andare an addition to the detailed description of the present invention.The disclosures of all patents, patent applications, and publicationscited herein are hereby incorporated by reference.

What is claimed is:
 1. A method of forming a composition comprisingcontacting (a) a fuel and (b) at least one compound characterized byFormula I:

wherein X can be carbon (C), oxygen (O), or sulfur (S); wherein, when Xis C, R¹ and R² can each independently be hydrogen, a C₁ to C₂₀ alkylgroup, or a C₆ to C₁₀ aryl group, and wherein the C₆ to C₁₀ aryl groupis a hydrocarbon; wherein, when X is O or S, R¹ and R² are lonenon-bonding electron pairs; R³ and R^(3′) can each independently behydrogen or a C₁ to C₄ alkyl group; R⁴ and R^(4′) can each independentlybe hydrogen, a C₁ to C₄ alkyl group, a C₄ to C₁₀ cycloalkyl group, or aC₆ to C₁₀ aryl group; R⁵ and R^(5′) can each independently be a C₄ toC₁₀ alkyl group; R⁶ and R^(6′) can each independently be hydrogen or aC₁ to C₆ alkyl group; and R⁷ and R^(7′) can each independently behydrogen or a C₁ to C₄ alkyl group; and wherein the compoundcharacterized by Formula I when subjected to gas chromatography—massspectrometry (GC-MS) using electron ionization produces at least one ionhaving a mass-to-charge ratio of from about 300 to about 600 at anionization energy of equal to or greater than about 70 eV.
 2. The methodof claim 1 wherein X is O and wherein the compound characterized byFormula I has Structure A:


3. The method of claim 1 wherein X is S and wherein the compoundcharacterized by Formula I has any of Structures B-F:


4. The method of claim 1 wherein X is C and R¹ and R² each independentlyare selected from the group consisting of a methyl group, an ethylgroup, a n-propyl group, an iso-propyl group, a n-butyl group, aniso-butyl group, a sec-butyl group, a tort-butyl group, a pentyl group,a n-pentyl group, an iso-pentyl group, a sec-pentyl group, a hexylgroup, a heptyl group, an octyl group, a nonyl group, a decyl group, aundecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, apentadecyl group, a hexadecyl group, a heptadecyl group, an octadecylgroup and a nonadecyl group.
 5. The method of claim 1 wherein thecompound characterized by Formula I has any of Structures G-O:


6. The method of claim 1 wherein X is C and R¹ and R² can eachindependently be hydrogen, a C₁ to C₁₀ alkyl group, or a C₆ to C₁₀ arylgroup.
 7. The method of claim 6 wherein the C₆ to C₁₀ aryl group isphenyl, a substituted phenyl, tolyl, a substituted tolyl, xylyl or asubstituted xylyl.
 8. The method of claim 6 wherein the compoundcharacterized by Formula I has Structure P:


9. The method of claim 1 wherein X is C and R³ and R^(3′) can eachindependently be a methyl group or hydrogen.
 10. The method of claim 1wherein X is C and R⁴, and R^(4′) can each independently be a C₁ to C₁₀alkyl group, a C₄ to C₁₀ cycloalkyl group, or a C₆ to C₁₀ aryl group.11. The method of claim 10 wherein R⁵ and R^(5′) are both a pentyl groupor a heptyl group.
 12. The method of claim 10 wherein the C₄ to C₁₀cycloalkyl group is a cyclobutyl group, a substituted cyclobutyl group,a cyclopentyl group, a substituted cyclopentyl group, a cyclohexylgroup, a substituted cyclohexyl group, a cycloheptyl group, asubstituted cycloheptyl group, a cyclooctyl group, or a substitutedcyclooctyl group.
 13. The method of claim 1 wherein X is C, R¹ and R²are a methyl group, and R⁵ and R^(5′) are both a C₄ to C₁₀ alkyl group.14. The method of claim 1 wherein the fuel comprises gasoline, diesel,jet fuel, kerosene, non-petroleum derived fuels, alcohol fuels, ethanol,methanol, propanol, butanol, biodiesel, maritime fuels, or combinationsthereof.
 15. The method of claim 1 wherein the compound characterized byFormula I is present in the composition in an amount of from about 1 ppbto about 50 ppm, based on the total weight of the composition.
 16. Themethod of claim 1 wherein the composition comprises at least 2 compoundscharacterized by Formula I.
 17. The method of claim 16 furthercomprising (i) acquiring a fuel sample; (ii) subjecting the fuel sampleto GC-MS to yield GC-MS data; and (iii) comparing the GC-MS data of thefuel sample with the GC-MS data of the composition.
 18. The method ofclaim 17 further comprising determining an amount of the compoundcharacterized by Formula I present in the composition and the fuelsample based on the GC-MS data.
 19. The method of claim 1 furthercomprising subjecting the composition to surface enhanced Ramanscattering spectroscopy.
 20. The method of claim 1 further comprisingsubjecting the composition to nuclear magnetic resonance spectroscopy.21. The method of claim 1 wherein R³ and R^(3′) are hydrogen.